test-release.sh: Default to letting ninja select the number of build jobs (#73187)

ninja defaults to using ncpus + 2 build jobs, and this extra parallelism
helps the script complete faster in my testing on the GitHub runners.

Author: tstellar

llvm/utils/release/test-release.sh

@@ -246,6 +246,8 @@ if [ "$Release" != "test" ]; then
   fi
 fi
 
+UserNumJobs="$NumJobs"
+
 # Figure out how many make processes to run.
 if [ -z "$NumJobs" ]; then
     NumJobs=`sysctl -n hw.activecpu 2> /dev/null || true`
@@ -260,6 +262,13 @@ if [ -z "$NumJobs" ]; then
     NumJobs=3
 fi
 
+if [ "$MAKE" = "ninja" ] && [ -z "$UserNumJobs" ]; then
+  # Rely on default ninja job numbers
+  J_ARG=""
+else
+  J_ARG="-j $NumJobs"
+fi
+
 # Projects list
 projects="llvm;clang"
 if [ $do_clang_tools = "yes" ]; then
@@ -484,8 +493,8 @@ function build_llvmCore() {
 
     cd $ObjDir
     echo "# Compiling llvm $Release-$RC $Flavor"
-    echo "# ${MAKE} -j $NumJobs $Verbose"
-    ${MAKE} -j $NumJobs $Verbose $BuildTarget \
+    echo "# ${MAKE} $J_ARG $Verbose"
+    ${MAKE} $J_ARG $Verbose $BuildTarget \
         2>&1 | tee $LogDir/llvm.make-Phase$Phase-$Flavor.log > $redir
 
     echo "# Installing llvm $Release-$RC $Flavor"
@@ -508,7 +517,7 @@ function test_llvmCore() {
     fi
 
     cd $ObjDir
-    if ! ( ${MAKE} -j $NumJobs $KeepGoing $Verbose check-all \
+    if ! ( ${MAKE} $J_ARG $KeepGoing $Verbose check-all \
         2>&1 | tee $LogDir/llvm.check-Phase$Phase-$Flavor.log ) ; then
       deferred_error $Phase $Flavor "check-all failed"
     fi
@@ -519,7 +528,7 @@ function test_llvmCore() {
           cmake $TestSuiteSrcDir -G "$generator" -DTEST_SUITE_LIT=$Lit \
                 -DTEST_SUITE_HOST_CC=$build_compiler
 
-      if ! ( ${MAKE} -j $NumJobs $KeepGoing $Verbose check \
+      if ! ( ${MAKE} $J_ARG $KeepGoing $Verbose check \
           2>&1 | tee $LogDir/llvm.check-Phase$Phase-$Flavor.log ) ; then
         deferred_error $Phase $Flavor "test suite failed"
       fi