gl: WARNING: The variable(s) GL_CFLAGS in the input file gstreamer-gl.pc.in are not present in the given configuration data.

.pc files differ between autoconf and meson build system

I tried building gst-plugins-base using meson instead of autoconf. Generally, this 'works', but the generated .pc file is missing relevant CFLAG entries, which makes other, dependent packages possibly fail.

Diff of autoconf vs meson generated .pc file (gstreamer-gl.pc - did not check all the others yet)

> diff -ur /usr/lib64/pkgconfig/gstreamer-gl-1.0.pc gstreamer-gl-1.0.pc 
--- /usr/lib64/pkgconfig/gstreamer-gl-1.0.pc	2020-02-07 20:44:37.000000000 +0100
+++ gstreamer-gl-1.0.pc	2020-03-05 18:26:19.000000000 +0100
@@ -1,11 +1,11 @@
 prefix=/usr
-exec_prefix=/usr
-libdir=/usr/lib64
-includedir=/usr/include/gstreamer-1.0
-pluginsdir=/usr/lib64/gstreamer-1.0
-gl_platforms=glx egl 
-gl_winsys=gbm wayland x11 
-gl_apis=gles2 gl 
+exec_prefix=${prefix}
+libdir=${prefix}/lib64
+includedir=${prefix}/include/gstreamer-1.0
+pluginsdir=${prefix}/lib64/gstreamer-1.0
+gl_platforms=egl glx
+gl_winsys=wayland x11 gbm
+gl_apis=gles2 gl
 
 Name: GStreamer OpenGL Plugins Libraries
 Description: Streaming media framework, OpenGL plugins libraries
@@ -13,4 +13,4 @@
 Requires: gstreamer-video-1.0 gstreamer-base-1.0 gstreamer-1.0
 
 Libs: -L${libdir} -lgstgl-1.0
-Cflags: -I${includedir} -I${libdir}/gstreamer-1.0/include  -I/usr/include/libdrm    -I/usr/include/wayland  
+Cflags: -I${includedir} -I${libdir}/gstreamer-1.0/include 

The Cflags is the critical one, as paths to other headers we relay on are not correctly added to the .pc file