Create and install pkg-config file

This hasn't been working since the switch away from waf.

Signed-off-by: Carlos Martín Nieto <carlos@cmartin.tk>

CMakeLists.txt

@@ -99,6 +99,7 @@ ENDIF ()
 TARGET_LINK_LIBRARIES(git2 ${CMAKE_THREAD_LIBS_INIT})
 SET_TARGET_PROPERTIES(git2 PROPERTIES VERSION ${LIBGIT2_VERSION_STRING})
 SET_TARGET_PROPERTIES(git2 PROPERTIES SOVERSION ${LIBGIT2_VERSION_MAJOR})
+CONFIGURE_FILE(libgit2.pc.in libgit2.pc)
 
 # Install
 INSTALL(TARGETS git2
@@ -106,6 +107,7 @@ INSTALL(TARGETS git2
     LIBRARY DESTINATION ${INSTALL_LIB}
     ARCHIVE DESTINATION ${INSTALL_LIB}
 )
+INSTALL(FILES libgit2.pc DESTINATION ${INSTALL_LIB}/pkgconfig )
 INSTALL(DIRECTORY include/git2 DESTINATION ${INSTALL_INC} )
 INSTALL(FILES include/git2.h DESTINATION ${INSTALL_INC} )
 

libgit2.pc.in

-prefix=@prefix@
-exec_prefix=${prefix}
-libdir=@libdir@
-includedir=${prefix}/include
+libdir=@CMAKE_INSTALL_PREFIX@/@INSTALL_LIB@
+includedir=@CMAKE_INSTALL_PREFIX@/@INSTALL_INC@
 
 Name: libgit2
 Description: The git library, take 2
-Version: @version@
+Version: @LIBGIT2_VERSION_STRING@
 Requires: libcrypto
 Libs: -L${libdir} -lgit2 -lz -lcrypto
 Cflags: -I${includedir}