* guix/build/meson-build-system.scm (configure): Test for LDFLAGS before adding ours.
* guix/build/meson-build-system.scm (configure): Set LDFLAGS before invoking meson.
* Makefile.am (MODULES): Add 'guix/build-system/meson.scm' and 'guix/build/meson-build-system.scm'. * guix/build-system/meson.scm: New file. * guix/build/meson-build-system.scm: New file. * doc/guix.texi (Build Systems): Add 'meson-build-system'. Signed-off-by: Ludovic Courtès <ludo@gnu.org>