internal/rosa: parallel cmake bootstrap

This takes a very long time otherwise.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/cmake.go

@@ -23,7 +23,9 @@ chmod -R +w /usr/src/cmake/Tests
 
 cd "$(mktemp -d)"
 /usr/src/cmake/bootstrap \
-	--prefix=/system -- \
+	--prefix=/system \
+	--parallel="$(nproc)" \
+	-- \
 	-DCMAKE_USE_OPENSSL=OFF
 make "-j$(nproc)"
 make DESTDIR=/work install