Add pkg-config support

.gitignore

@@ -70,3 +70,4 @@ win/x64
 win/x85
 win/Debug
 cglm-test-ios*
+/cglm.pc

cglm.pc.in

@@ -0,0 +1,11 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: @PACKAGE_NAME@
+Description: OpenGL Mathematics (glm) for C
+URL: https://github.com/recp/cglm
+Version: @PACKAGE_VERSION@
+Cflags: -I${includedir}
+Libs: -L${libdir} -lcglm @LIBS@

configure.ac

@@ -14,6 +14,10 @@ AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_SRCDIR([src/])
 AC_CONFIG_HEADERS([config.h])
 
+# Dependencies for pkg-config.
+PKG_PROG_PKG_CONFIG
+PKG_INSTALLDIR
+
 # Checks for programs.
 AC_PROG_CC
 AM_PROG_CC_C_O
@@ -53,6 +57,6 @@ AC_TYPE_UINT8_T
 # Checks for library functions.
 AC_FUNC_ERROR_AT_LINE
 
-AC_CONFIG_FILES([makefile])
+AC_CONFIG_FILES([makefile cglm.pc])
 
 AC_OUTPUT

makefile.am

@@ -154,6 +154,8 @@ test_tests_SOURCES=\
     test/src/test_affine.c \
     test/src/test_bezier.c
 
+pkgconfig_DATA=cglm.pc
+
 # When running configure with --prefix, $VPATH references
 # the source directory that post-build.sh is in. When not
 # using a prefix, $VPATH will be unset, so we need to fall