automake: create compat symlinks only for linux systems

The primary users of these are linux developers, although
it can be extended for *BSD and others if needed.

Fixes make install for Cygwin and OpenBSD at least.

v2:
 - Wrap vdpau targets as well.
v3:
 - Fold HAVE_COMPAT_SYMLINKS conditional within install*links.mk

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=63269
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jon TURNEY <jon.turney@dronecode.org.uk> (v1)
Reviewed-by: Christian König <christian.koenig@amd.com>
diff --git a/configure.ac b/configure.ac
index 5e1d091..0735a76 100644
--- a/configure.ac
+++ b/configure.ac
@@ -317,6 +317,18 @@
 fi
 
 dnl
+dnl compatibility symlinks
+dnl
+case "$host_os" in
+linux* )
+    HAVE_COMPAT_SYMLINKS=yes ;;
+* )
+    HAVE_COMPAT_SYMLINKS=no ;;
+esac
+
+AM_CONDITIONAL(HAVE_COMPAT_SYMLINKS, test "x$HAVE_COMPAT_SYMLINKS" = xyes)
+
+dnl
 dnl library names
 dnl
 if test "$enable_static" = yes; then