community/mercury: use $JOBS instead of $MAKEFLAGS for $PARALLEL

$PARALLEL is passed to Mercury's build tool mmc, $MAKEFLAGS may
contain command-line options not supported by mmc. Therefore, it
is preferable to use $JOBS over $MAKEFLAGS.

community/mercury/APKBUILD

@@ -33,7 +33,7 @@ build() {
 		--with-llds-base-grade=fast \
 		--enable-libgrades="hlc.gc"
 
-	make PARALLEL="$MAKEFLAGS"
+	make PARALLEL="-j${JOBS:-1}"
 }
 
 package() {
@@ -43,7 +43,7 @@ package() {
 		INSTALL_INFO_DIR="$pkgdir"/usr/share/info \
 		MERCURY_COMPILER="$pkgdir"/usr/bin/mercury_compile \
 		MERCURY_CONFIG_DIR="$pkgdir"/usr/lib/mercury \
-		PARALLEL="$MAKEFLAGS" \
+		PARALLEL="-j${JOBS:-1}" \
 		install
 
 	rm "$pkgdir"/usr/lib/mercury/lib/hlc.gc/libmer_*.a