cmake: add an option to control dependencies vendoring

Disable by default, to be used by distributions who care to try and
prefer system-wide libraries when available. It makes sense for us to
keep using vendored libs by default when possible to make it easier for
users to compile, but we should provide appropriate tools for distro to
figure out which dependencies they can share with the rest of the
system.

CMake/CheckVendoringApproved.cmake

@@ -0,0 +1,29 @@
+# When packaging Dolphin for an OS distribution, distro vendors usually prefer
+# to limit vendored ("Externals") dependencies as much as possible, in favor of
+# using system provided libraries. This modules provides an option to allow
+# only specific vendored dependencies and error-out at configuration time for
+# non-approved ones.
+#
+# Usage:
+#  $ cmake -D APPROVED_VENDORED_DEPENDENCIES="a;b;c;..."
+#
+# Unless the option is explicitly used, vendored dependencies control is
+# disabled.
+#
+# If you want to disallow all vendored dependencies, put "none" in the approved
+# dependencies list.
+
+set(APPROVED_VENDORED_DEPENDENCIES "" CACHE STRING "\
+Semicolon separated list of approved vendored dependencies. See docstring in \
+CMake/CheckVendoringApproved.cmake.")
+
+function(check_vendoring_approved dep)
+  if(APPROVED_VENDORED_DEPENDENCIES)
+    if(NOT dep IN_LIST APPROVED_VENDORED_DEPENDENCIES)
+      message(SEND_ERROR "\
+Library ${dep} was not found systemwide and was not approved for vendoring. \
+Vendored dependencies control is enabled. Add \"${dep}\" to the \
+APPROVED_VENDORED_DEPENDENCIES list to bypass this error.")
+    endif()
+  endif()
+endfunction()

CMakeLists.txt

@@ -88,6 +88,7 @@ list(APPEND CMAKE_MODULE_PATH
 # Support functions
 include(CheckAndAddFlag)
 include(CheckCCompilerFlag)
+include(CheckVendoringApproved)
 include(DolphinCompileDefinitions)
 
 # Enable folders for IDE
@@ -536,6 +537,7 @@ find_package(fmt 6.0)
 if(fmt_FOUND)
   message(STATUS "Using shared fmt ${fmt_VERSION}")
 else()
+  check_vendoring_approved(fmt)
   message(STATUS "Using static fmt from Externals")
   add_subdirectory(Externals/fmt EXCLUDE_FROM_ALL)
 endif()
@@ -544,6 +546,7 @@ add_subdirectory(Externals/imgui)
 
 find_package(pugixml)
 if(NOT pugixml_FOUND)
+  check_vendoring_approved(pugixml)
   message(STATUS "Using static pugixml from Externals")
   add_subdirectory(Externals/pugixml)
 endif()
@@ -570,6 +573,7 @@ endif()
 if (ENET_FOUND)
   message(STATUS "Using shared enet")
 else()
+  check_vendoring_approved(enet)
   message(STATUS "Using static enet from Externals")
   include_directories(Externals/enet/include)
   add_subdirectory(Externals/enet)
@@ -584,6 +588,7 @@ find_package(BZip2)
 if(BZIP2_FOUND)
   message(STATUS "Using shared bzip2")
 else()
+  check_vendoring_approved(bzip2)
   message(STATUS "Shared bzip2 not found, falling back to the static library")
   add_subdirectory(Externals/bzip2)
 endif()
@@ -594,6 +599,7 @@ check_include_file(lzma.h HAVE_LZMA_H)
 if(LIBLZMA_FOUND AND HAVE_LZMA_H)
   message(STATUS "Using shared lzma")
 else()
+  check_vendoring_approved(lzma)
   if(LIBLZMA_FOUND AND NOT HAVE_LZMA_H)
     message(STATUS "Shared lzma found but lacks headers, falling back to the static library")
   else()
@@ -606,6 +612,7 @@ find_package(ZLIB)
 if(ZLIB_FOUND)
   message(STATUS "Using shared zlib")
 else()
+  check_vendoring_approved(zlib)
   message(STATUS "Shared zlib not found, falling back to the static library")
   add_subdirectory(Externals/zlib)
 endif()
@@ -614,6 +621,7 @@ pkg_check_modules(MINIZIP minizip>=2.0.0)
 if(MINIZIP_FOUND)
   message(STATUS "Using shared minizip")
 else()
+  check_vendoring_approved(minizip)
   message(STATUS "Shared minizip not found, falling back to the static library")
   add_subdirectory(Externals/minizip)
   include_directories(External/minizip)
@@ -625,6 +633,7 @@ endif()
 if(LZO_FOUND)
   message(STATUS "Using shared lzo")
 else()
+  check_vendoring_approved(lzo)
   message(STATUS "Using static lzo from Externals")
   add_subdirectory(Externals/LZO)
   set(LZO lzo2)
@@ -636,6 +645,7 @@ endif()
 if (PNG_FOUND)
   message(STATUS "Using shared libpng")
 else()
+  check_vendoring_approved(libpng)
   message(STATUS "Using static libpng from Externals")
   add_subdirectory(Externals/libpng)
   set(PNG png)
@@ -661,6 +671,7 @@ find_package(Cubeb)
 if(CUBEB_FOUND)
   message(STATUS "Using the system cubeb")
 else()
+  check_vendoring_approved(cubeb)
   message(STATUS "Using static cubeb from Externals")
   add_subdirectory(Externals/cubeb EXCLUDE_FROM_ALL)
 endif()
@@ -674,6 +685,7 @@ if(NOT ANDROID)
     message(STATUS "Using shared LibUSB")
     include_directories(${LIBUSB_INCLUDE_DIR})
   else()
+    check_vendoring_approved(libusb)
     message(STATUS "Using static LibUSB from Externals")
     add_subdirectory(Externals/libusb)
     set(LIBUSB_LIBRARIES usb)
@@ -688,6 +700,7 @@ endif()
 if(SFML_FOUND)
   message(STATUS "Using shared SFML")
 else()
+  check_vendoring_approved(sfml)
   message(STATUS "Using static SFML ${SFML_REQD_VERSION} from Externals")
   add_definitions(-DSFML_STATIC)
   add_subdirectory(Externals/SFML)
@@ -701,6 +714,7 @@ if(USE_UPNP)
   if(MINIUPNPC_FOUND AND MINIUPNPC_API_VERSION GREATER 8)
     message(STATUS "Using shared miniupnpc")
   else()
+    check_vendoring_approved(miniupnpc)
     message(STATUS "Using static miniupnpc from Externals")
     add_subdirectory(Externals/miniupnpc)
   endif()
@@ -714,6 +728,7 @@ if(MBEDTLS_FOUND)
   message(STATUS "Using shared mbed TLS")
   include_directories(${MBEDTLS_INCLUDE_DIRS})
 else()
+  check_vendoring_approved(mbedtls)
   message(STATUS "Using static mbed TLS from Externals")
   set(MBEDTLS_LIBRARIES mbedtls mbedcrypto mbedx509)
   add_subdirectory(Externals/mbedtls/ EXCLUDE_FROM_ALL)
@@ -725,6 +740,7 @@ if(CURL_FOUND)
   message(STATUS "Using shared libcurl")
   include_directories(${CURL_INCLUDE_DIRS})
 else()
+  check_vendoring_approved(curl)
   message(STATUS "Using static libcurl from Externals")
   add_subdirectory(Externals/curl)
   set(CURL_LIBRARIES curl)
@@ -739,6 +755,7 @@ endif()
 if (NOT ANDROID AND ICONV_LIBRARIES AND ICONV_INCLUDE_DIR)
   mark_as_advanced(ICONV_INCLUDE_DIR ICONV_LIBRARIES)
 else()
+  check_vendoring_approved(iconv)
   message(STATUS "Using static iconv from Externals")
   include_directories(Externals/libiconv-1.14/include)
   add_subdirectory(Externals/libiconv-1.14)
@@ -748,6 +765,7 @@ endif()
 if(NOT ANDROID)
   find_package(HIDAPI)
   if(NOT HIDAPI_FOUND)
+    check_vendoring_approved(hidapi)
     message(STATUS "Using static HIDAPI from Externals")
     add_subdirectory(Externals/hidapi EXCLUDE_FROM_ALL)
   endif()