Fix __NumProc setup if nproc is not available (#51002)

diff --git a/eng/native/build-commons.sh b/eng/native/build-commons.sh
index 63ffbba..e8f0b44 100755 (executable)
--- a/eng/native/build-commons.sh
+++ b/eng/native/build-commons.sh
@@ -282,7 +282,11 @@ elif [[ "$platform" == "NetBSD" || "$platform" == "SunOS" ]]; then
 elif [[ "$platform" == "Darwin" ]]; then
   __NumProc=$(($(getconf _NPROCESSORS_ONLN)+1))
 else
-  __NumProc=$(nproc --all)
+  if command -v nproc > /dev/null 2>&1; then
+    __NumProc=$(nproc --all)
+  else
+    __NumProc=1
+  fi
 fi
 
 while :; do