CI: Use Ninja to speed up compile times

Ninja should automatically run the appropriate amount of parallel jobs.

Also removed the --parallel from the README.md, since the default
generator (Unix Makefiles) is not smart about this and risks locking up
people's systems because the many compile jobs can make it run out of
memory.

1 files changed, 1 insertions, 1 deletions

diff --git a/README.md b/README.md
index 14e03fb1..605b682c 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,7 @@ Installing the dependencies on Fedora:
 Once the dependencies are installed, use CMake:
 
     cmake -B build .
-    cmake --build build --parallel
+    cmake --build build
 
 This produces an executable in `build/src/mana`. If running it without
 installing, be sure to run it from the repository root so that it can find its