configure: Automatically detect the default xorg-module-dir.

The module directory has changed to a per ABI folder in the xlibre-xserver.
Now the default value of `xorg-module-dir` will be detected from the `moduledir` variable in xorg-server.pc.

Signed-off-by: b-aaz <b-aazbsd.proton.me>

Makefile.am

@@ -20,6 +20,10 @@
 #  OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 #  USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+# During distcheck, system locations (as provided by pkg-config) may
+# not be writable; provide instead relative locations.
+DISTCHECK_CONFIGURE_FLAGS = --with-xorg-module-dir='$${libdir}/xorg/modules'
+
 SUBDIRS = src man
 MAINTAINERCLEANFILES = ChangeLog INSTALL
 .PHONY: ChangeLog INSTALL

configure.ac

@@ -51,9 +51,12 @@ LT_INIT([disable-static])
 AH_TOP([#include "xorg-server.h"])
 
 # Define a configure option for an alternate module directory
-AC_ARG_WITH(xorg-module-dir, [  --with-xorg-module-dir=DIR ],
-                             [ moduledir="$withval" ],
-                             [ moduledir="$libdir/xorg/modules" ])
+PKG_PROG_PKG_CONFIG([0.25])
+AC_ARG_WITH(xorg-module-dir,
+            AS_HELP_STRING([--with-xorg-module-dir=DIR],
+                           [Default xorg module directory]),
+            [moduledir="$withval"],
+            [moduledir=`$PKG_CONFIG --variable=moduledir xorg-server`])
 AC_SUBST(moduledir)
 
 # Store the list of server defined optional extensions in REQUIRED_MODULES