Fix pkg-config generation

this fixes #25

Author: paolostivanin

CMakeLists.txt

@@ -9,7 +9,7 @@ add_subdirectory(tests)
 # set up versioning.
 set(BUILD_MAJOR "1")
 set(BUILD_MINOR "0")
-set(BUILD_VERSION "13")
+set(BUILD_VERSION "14")
 set(BUILD_VERSION ${BUILD_MAJOR}.${BUILD_MINOR}.${BUILD_VERSION})
 
 set(CMAKE_C_STANDARD 11)
@@ -40,5 +40,18 @@ install(
   DESTINATION ${BASEENCODE_INC_DIR}
 )
 
+# Allow adding prefix if CMAKE_INSTALL_INCLUDEDIR not absolute.
+if(IS_ABSOLUTE "${CMAKE_INSTALL_INCLUDEDIR}")
+    set(PKGCONFIG_TARGET_INCLUDES "${CMAKE_INSTALL_INCLUDEDIR}")
+else()
+    set(PKGCONFIG_TARGET_INCLUDES "\${prefix}/${CMAKE_INSTALL_INCLUDEDIR}")
+endif()
+# Allow adding prefix if CMAKE_INSTALL_LIBDIR not absolute.
+if(IS_ABSOLUTE "${CMAKE_INSTALL_LIBDIR}")
+    set(PKGCONFIG_TARGET_LIBS "${CMAKE_INSTALL_LIBDIR}")
+else()
+    set(PKGCONFIG_TARGET_LIBS "\${exec_prefix}/${CMAKE_INSTALL_LIBDIR}")
+endif()
+
 configure_file("baseencode.pc.in" "baseencode.pc" @ONLY)
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/baseencode.pc" DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig/)

baseencode.pc.in

@@ -1,5 +1,11 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+libdir=@PKGCONFIG_TARGET_LIBS@
+includedir=@PKGCONFIG_TARGET_INCLUDES@
+
 Name: libbaseencode
 Description: C library for encoding and decoding data using base32 or base64
 Version: @BUILD_VERSION@
-Libs: -L@CMAKE_INSTALL_PREFIX@/@BASEENCODE_LIB_DIR@ -lbaseencode
-Cflags: -I@CMAKE_INSTALL_PREFIX@/@BASEENCODE_INC_DIR@
+URL: https://github.com/paolostivanin/libbaseencode
+Libs: -L${libdir} -lbaseencode
+Cflags: -I${includedir}