main/gcc: add pkgrel info into version output

this makes gcc --version output also contain the pkgrel, which can
sometimes be useful

main/gcc/APKBUILD

@@ -356,7 +356,7 @@ build() {
 		--build=${CBUILD} \
 		--host=${CHOST} \
 		--target=${CTARGET} \
-		--with-pkgversion="Alpine $pkgver" \
+		--with-pkgversion="Alpine $pkgver-r$pkgrel" \
 		--enable-checking=release \
 		--disable-fixed-point \
 		--disable-libstdcxx-pch \