speed up build for my slow laptop

bin/build-all.sh

@@ -14,6 +14,8 @@ BOARDS_ESP32="tlora-v2 tlora-v1 tlora-v2-1-1.6 tbeam heltec tbeam0.7"
 # FIXME note nrf52840dk build is for some reason only generating a BIN file but not a HEX file nrf52840dk-geeksville is fine
 BOARDS_NRF52="lora-relay-v1"
 
+NUM_JOBS=2
+
 OUTDIR=release/latest
 
 # We keep all old builds (and their map files in the archive dir)
@@ -49,7 +51,7 @@ function do_build() {
         basename=universal/firmware-$BOARD-$VERSION
     fi
 
-    pio run --jobs 4 --environment $BOARD # -v
+    pio run --jobs $NUM_JOBS --environment $BOARD # -v
     SRCELF=.pio/build/$BOARD/firmware.elf
     cp $SRCELF $OUTDIR/elfs/$basename.elf