Limit number of make job to actuall number of processors, gracefully handle invalid values for CONCURRENCY_MAKE_LEVEL

limit-concurrency.diff

diff --git a/config/path b/config/path
index 78f53d5..9043ddc 100644
--- a/config/path
+++ b/config/path
@@ -52,6 +52,11 @@ ROOT=`pwd`
 # Toolchain Settings #
 ######################
 
+NUM_PROCESSORS=`grep -c processor /proc/cpuinfo`
+[ -z "$CONCURRENCY_MAKE_LEVEL" ] && CONCURRENCY_MAKE_LEVEL=0
+[ $CONCURRENCY_MAKE_LEVEL -lt 1 -o $CONCURRENCY_MAKE_LEVEL -gt $NUM_PROCESSORS ] && \
+  CONCURRENCY_MAKE_LEVEL=$NUM_PROCESSORS
+
 . config/toolchain
 
 TOOLCHAIN_LANGUAGES=c