zathura-pdf-mupdf: fix CFLAGS and LDFLAGS

srcpkgs/zathura-pdf-mupdf/template

@@ -14,6 +14,11 @@ short_desc="PDF support for zathura (using mupdf)"
 distfiles="http://pwmt.org/projects/${pkgname}/download/${pkgname}-${version}.tar.gz"
 checksum=b1343f35940ebcf463b868b557be4eaba7d61884d6ff3ad3d7c7c272e69c253f
 
+pre_build() {
+	sed -i 's/^\(CFLAGS *+=\)/override \1/' config.mk
+	sed -i 's/^\(LDFLAGS *+=\)/override \1/' config.mk
+}
+
 post_install() {
 	vlicense LICENSE
 }