qmake: Use pkgconfig feature

Instead of using r2 to get the lib and include paths use the builtin
qmake feature for pkgconfig. Still needs a tweak to work with
sys/user.sh installations.

src/lib_radare2.pri

@@ -8,48 +8,39 @@ win32 {
     } else {
         LIBS += -L"$$PWD/../iaito_win32/radare2/lib64"
     }
+
+    LIBS += \
+        -lr_core \
+        -lr_config \
+        -lr_cons \
+        -lr_io \
+        -lr_util \
+        -lr_flag \
+        -lr_asm \
+        -lr_debug \
+        -lr_hash \
+        -lr_bin \
+        -lr_lang \
+        -lr_io \
+        -lr_anal \
+        -lr_parse \
+        -lr_bp \
+        -lr_egg \
+        -lr_reg \
+        -lr_search \
+        -lr_syscall \
+        -lr_socket \
+        -lr_fs \
+        -lr_magic \
+        -lr_crypto
 } else {
-    # check if r2 is available
-    system(r2 > /dev/null 2>&1) {
-
-        # see https://github.com/hteso/iaito/pull/5#issuecomment-290433796
-        RADARE2_INCLUDE_PATH = $$system(r2 -H | grep INCDIR | sed 's/[^=]*=//')
-        RADARE2_LIB_PATH = $$system(r2 -H | grep LIBDIR | sed 's/[^=]*=//')
-
-        !isEmpty(RADARE2_INCLUDE_PATH) {
-            INCLUDEPATH *= $$RADARE2_INCLUDE_PATH
-            LIBS *= -L$$RADARE2_LIB_PATH
-        } else {
-            error("sorry could not find radare2 lib")
-        }
-    } else {
-        error("r2 not found/in path")
+    R2_USER_PKGCONFIG = $$(HOME)/bin/prefix/radare2/lib/pkgconfig
+    exists($$R2_USER_PKGCONFIG) {
+        # caution: may not work for cross compilations
+        QMAKE_PKG_CONFIG = PKG_CONFIG_PATH=$$R2_USER_PKGCONFIG pkg-config
     }
+
+    CONFIG += link_pkgconfig
+    PKGCONFIG += r_core
 }
 
-
-LIBS += \
-    -lr_core \
-    -lr_config \
-    -lr_cons \
-    -lr_io \
-    -lr_util \
-    -lr_flag \
-    -lr_asm \
-    -lr_debug \
-    -lr_hash \
-    -lr_bin \
-    -lr_lang \
-    -lr_io \
-    -lr_anal \
-    -lr_parse \
-    -lr_bp \
-    -lr_egg \
-    -lr_reg \
-    -lr_search \
-    -lr_syscall \
-    -lr_socket \
-    -lr_fs \
-    -lr_magic \
-    -lr_crypto
-