ENH: add a cmake module for using pkg-config, tested in kdelibs, ok by Bill Hoffman

Alex

Modules/UsePkgConfig.cmake

@@ -0,0 +1,40 @@
+# - pkg-config module for CMake
+# Defines the following macros:
+#   PKGCONFIG(package includedir libdir linkflags cflags)
+#     - Calling PKGCONFIG will fill the desired information into the 4 given arguments,
+#       e.g. PKGCONFIG(libart-2.0 LIBART_INCLUDE_DIR LIBART_LINK_DIR LIBART_LINK_FLAGS LIBART_CFLAGS)
+#      if pkg-config was NOT found or the specified software package doesn't exist, the
+#      variable will be empty when the function returns, otherwise they will contain the respective information
+
+FIND_PROGRAM(PKGCONFIG_EXECUTABLE NAMES pkg-config PATHS /usr/local/bin )
+
+MACRO(PKGCONFIG _package _include_DIR _link_DIR _link_FLAGS _cflags)
+# reset the variables at the beginning
+  SET(${_include_DIR})
+  SET(${_link_DIR})
+  SET(${_link_FLAGS})
+  SET(${_cflags})
+
+  # if pkg-config has been found
+  IF(PKGCONFIG_EXECUTABLE)
+
+    EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --exists RETURN_VALUE _return_VALUE OUTPUT_VARIABLE _pkgconfigDevNull )
+
+    # and if the package of interest also exists for pkg-config, then get the information
+    IF(NOT _return_VALUE)
+
+      EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --variable=includedir OUTPUT_VARIABLE ${_include_DIR} )
+
+      EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --variable=libdir OUTPUT_VARIABLE ${_link_DIR} )
+
+      EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --libs OUTPUT_VARIABLE ${_link_FLAGS} )
+
+      EXEC_PROGRAM(${PKGCONFIG_EXECUTABLE} ARGS ${_package} --cflags OUTPUT_VARIABLE ${_cflags} )
+
+    ENDIF(NOT _return_VALUE)
+
+  ENDIF(PKGCONFIG_EXECUTABLE)
+
+ENDMACRO(PKGCONFIG _include_DIR _link_DIR _link_FLAGS _cflags)
+
+MARK_AS_ADVANCED(PKGCONFIG_EXECUTABLE)