gallium/osmesa: Make and install an osmesa.pc.

As of "2f142d59 build: Add --enable-gallium-osmesa flag." the pkgconfig
file from classic osmesa is no longer installed when building gallium
osmesa, so copy it to gallium osmesa and install the copy instead.

CC: "9.2" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
(cherry picked from commit c811190430)

configure.ac

@@ -2066,6 +2066,7 @@ AC_CONFIG_FILES([Makefile
 		src/gallium/targets/gbm/Makefile
 		src/gallium/targets/opencl/Makefile
 		src/gallium/targets/osmesa/Makefile
+		src/gallium/targets/osmesa/osmesa.pc
 		src/gallium/targets/pipe-loader/Makefile
 		src/gallium/targets/libgl-xlib/Makefile
 		src/gallium/targets/vdpau-nouveau/Makefile

src/gallium/targets/osmesa/Makefile.am

@@ -85,6 +85,5 @@ all-local: lib@OSMESA_LIB@.la
 	cp .libs/lib@OSMESA_LIB@.so.@OSMESA_VERSION@.0.0 $(top_builddir)/$(LIB_DIR)/gallium/
 endif
 
-# XXX fix-up?
-#pkgconfigdir = $(libdir)/pkgconfig
-#pkgconfig_DATA = osmesa.pc
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = osmesa.pc

src/gallium/targets/osmesa/osmesa.pc.in

@@ -0,0 +1,12 @@
+prefix=@prefix@
+exec_prefix=${prefix}
+libdir=@libdir@
+includedir=@includedir@
+
+Name: osmesa
+Description: Mesa Off-screen Rendering library
+Requires: @OSMESA_PC_REQ@
+Version: @OSMESA_VERSION@
+Libs: -L${libdir} -l@OSMESA_LIB@
+Libs.private: @OSMESA_PC_LIB_PRIV@
+Cflags: -I${includedir}