Allows passing --load-average and not passing --jobs which would stop the jobserver from working.

This is a Gentoo'ism so its not upstreamable in this form.

diff --git a/build_scripts/main.py b/build_scripts/main.py
index cdaa439ff..3e088961e 100644
--- a/build_scripts/main.py
+++ b/build_scripts/main.py
@@ -854,8 +854,8 @@ class PysideBuild(_build, CommandMixin, BuildInfoCollectorMixin):
 
         log.info(f"-- Compiling module {extension}...")
         cmd_make = [str(self.make_path)]
-        if OPTION["JOBS"]:
-            cmd_make.append(OPTION["JOBS"])
+        if self.make_generator == "Ninja":
+            cmd_make.extend(os.getenv("NINJAOPTS").split(' '))
         if OPTION["LOG_LEVEL"] == LogLevel.VERBOSE and self.make_generator == "Ninja":
             cmd_make.append("-v")
         if run_process(cmd_make) != 0: