Allow to limit number of cores used for compilation

.build.yml

@@ -2,4 +2,4 @@ pipeline:
   build:
     image: codingworkshop/oscw-runner:latest
     commands:
-      - ./build-linux.sh
+      - CORES=8 ./build-linux.sh

build-linux.sh

@@ -508,9 +508,11 @@ xtchain_build()
 set -e
 
 # Check number of CPU cores available
-: ${CORES:=$(sysctl -n hw.ncpu 2>/dev/null)}
-: ${CORES:=$(nproc 2>/dev/null)}
-: ${CORES:=1}
+if [[ ! -n ${CORES} ]]; then
+	: ${CORES:=$(sysctl -n hw.ncpu 2>/dev/null)}
+	: ${CORES:=$(nproc 2>/dev/null)}
+	: ${CORES:=1}
+fi
 
 # Create working directories
 mkdir -p ${BINDIR}