meson: fix logic for generating .pc files with old glvnd

We want to generate PC files for non-glvnd builds and for builds with
old glvnd, but the current logic doesn't do that, it builds them
unconditionally, and for GLES it builds the shared libraries, which is
also not what we want. This does not generate .pc files for gles1 or
gles2. Which it we weren't doing before either, making this not a
regression but a return to status-quo.o

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1838
Fixes: 93df862b6affb6b8507e40601212a58012bfa873
       ("meson: re-add incorrect pkg-config files with GLVND for backward compatibility")
Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/meson.build b/meson.build
index 0e46fde..da4a075 100644
--- a/meson.build
+++ b/meson.build
@@ -100,7 +100,7 @@
 
 # shared-glapi is required if at least two OpenGL APIs are being built
 if not with_shared_glapi
-  if ((with_gles1 == 'true' and with_gles2 == 'true') or 
+  if ((with_gles1 == 'true' and with_gles2 == 'true') or
       (with_gles1 == 'true' and with_opengl) or
       (with_gles2 == 'true' and with_opengl))
     error('shared-glapi required for building two or more of OpenGL, OpenGL ES 1.x, OpenGL ES 2.x')
@@ -397,7 +397,7 @@
 if with_glx != 'disabled'
   if not (with_platform_x11 and with_any_opengl)
     error('Cannot build GLX support without X11 platform support and at least one OpenGL API')
-  elif with_glx == 'gallium-xlib' 
+  elif with_glx == 'gallium-xlib'
     if not with_gallium
       error('Gallium-xlib based GLX requires at least one gallium driver')
     elif not with_gallium_softpipe
@@ -405,7 +405,7 @@
     elif with_dri
       error('gallium-xlib conflicts with any dri driver')
     endif
-  elif with_glx == 'xlib' 
+  elif with_glx == 'xlib'
     if with_dri
       error('xlib conflicts with any dri driver')
     endif
@@ -1326,6 +1326,7 @@
 endif
 
 dep_glvnd = null_dep
+glvnd_missing_pc_files = false
 if with_glvnd
   dep_glvnd = dependency('libglvnd', version : '>= 0.2.0')
   # GLVND until commit 0dfaea2bcb7cdcc785f9 ("Add pkg-config files for EGL, GL,
@@ -1462,7 +1463,7 @@
   if with_glx == 'dri' or with_glx == 'gallium-xlib'
     dep_glproto = dependency('glproto', version : '>= 1.4.14')
   endif
-  if with_glx == 'dri' 
+  if with_glx == 'dri'
     if with_dri_platform == 'drm'
       dep_dri2proto = dependency('dri2proto', version : '>= 2.8')
       dep_xxf86vm = dependency('xxf86vm')