Write and install pkg-config file

tinyobjloader.pc.in

@@ -0,0 +1,15 @@
+# Generated by CMake @CMAKE_VERSION@ for @PROJECT_NAME@. Any changes to this
+# file will be overwritten by the next CMake run. The input file was
+# tinyobjloader.pc.in.
+
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+libdir=${prefix}/@TINYOBJLOADER_LIBRARY_DIR@
+includedir=${prefix}/@TINYOBJLOADER_INCLUDE_DIR@
+
+Name: @PROJECT_NAME@
+Description: Tiny but powerful single file wavefront obj loader
+URL: https://syoyo.github.io/tinyobjloader/
+Version: @TINYOBJLOADER_VERSION@
+Libs: -L${libdir} -ltinyobjloader
+Cflags: -I${includedir}