Check the presence of the submodules (#19)

Taken from here: https://github.com/yuzu-emu/yuzu/blob/master/CMakeLists.txt

CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.8)
+project(Vita3K)
+
+add_subdirectory(src/external)
+add_subdirectory(src/emulator)
+add_subdirectory(src/gen-modules)

gen.bat

@@ -1,4 +1,4 @@
 mkdir build-windows
 pushd build-windows
-cmake -G "Visual Studio 15 2017 Win64" ../src
+cmake -G "Visual Studio 15 2017 Win64" ..
 popd

gen.sh

@@ -3,4 +3,4 @@ set -ex
 
 mkdir -p build-macos
 cd build-macos
-cmake -G Xcode ../src
+cmake -G Xcode ..

src/CMakeLists.txt

@@ -1,6 +0,0 @@
-cmake_minimum_required(VERSION 3.8)
-project(Vita3K)
-
-add_subdirectory(external)
-add_subdirectory(emulator)
-add_subdirectory(gen-modules)

src/external/CMakeLists.txt

@@ -1,3 +1,16 @@
+function(check_submodules_present)
+    file(READ "${CMAKE_SOURCE_DIR}/.gitmodules" gitmodules)
+    string(REGEX MATCHALL "path *= *[^ \t\r\n]*" gitmodules ${gitmodules})
+    foreach(module ${gitmodules})
+        string(REGEX REPLACE "path *= *" "" module ${module})
+        if (NOT EXISTS "${CMAKE_SOURCE_DIR}/${module}/.git")
+            message(FATAL_ERROR "Git submodule ${module} not found. "
+                    "Please run: git submodule update --init --recursive")
+        endif()
+    endforeach()
+endfunction()
+check_submodules_present()
+
 option(CAPSTONE_BUILD_SHARED "Build shared library" OFF)
 option(CAPSTONE_BUILD_TESTS "Build tests" OFF)
 option(CAPSTONE_ARM_SUPPORT "ARM support" ON)