build_all.sh: building csources 5X faster thanks to make -j

build_all.sh

@@ -1,6 +1,7 @@
 #! /bin/sh
 
-# build development version of the compiler; can be rerun safely
+# build development version of the compiler; can be rerun safely.
+# arguments can be passed, eg `--cpu i386`
 
 set -u # error on undefined variables
 set -e # exit on first error
@@ -10,14 +11,20 @@ echo_run(){
   "$@"
 }
 
-[ -d csources ] || echo_run git clone --depth 1 https://github.com/nim-lang/csources.git
+[ -d csources ] || echo_run git clone -q --depth 1 https://github.com/nim-lang/csources.git
 
 nim_csources=bin/nim_csources
 build_nim_csources(){
   ## avoid changing dir in case of failure
   (
-    echo_run cd csources
-    echo_run sh build.sh $@
+    if [[ $# -ne 0 ]]; then
+      # some args were passed (eg: `--cpu i386`), need to call build.sh
+      echo_run cd csources
+      echo_run sh build.sh $@
+    else
+      # no args, use multhreaded (5X faster on 16 cores: 10s instead of 50s)
+      echo_run make -C csources -j
+    fi
   )
   # keep $nim_csources in case needed to investigate bootstrap issues
   # without having to rebuild from csources