chromium: really fix gn build

srcpkgs/chromium/template

@@ -223,11 +223,12 @@ do_configure() {
 		aarch64*) conf+=( 'target_cpu="arm64"' ) ;;
 	esac
 
+	export LDFLAGS="-pthread"
+
 	AR="ar" CC=$CC_FOR_BUILD CXX=$CXX_FOR_BUILD LD=$CXX_FOR_BUILD \
 	python2 tools/gn/bootstrap/bootstrap.py -s -v \
 		--gn-gen-args "${conf[*]}"
 
-	export LDFLAGS="-pthread"
 
 	out/Release/gn gen out/Release --args="${conf[*]}"
 }