scripts: Allow passing make flags to git-update.sh

Mostly adding this for add a -jN as appropriate while building.

scripts/git-update.sh

@@ -18,6 +18,8 @@ EXTRA_MODULES="\
     gst-rtsp-server \
     gst-python"
 
+MAKE_FLAGS=
+
 tmp=${TMPDIR-/tmp}
 tmp=$tmp/git-update.$(date +%Y%m%d-%H%M-).$RANDOM.$RANDOM.$RANDOM.$$
 
@@ -91,7 +93,7 @@ build()
     fi
 
     echo "+ $1: make"
-    make > "$tmp/$1-make.log" 2>&1
+    make $MAKE_FLAGS > "$tmp/$1-make.log" 2>&1
     if test $? -ne 0
     then
       echo "$1: make [$tmp/$1-make.log]" >> $ERROR_LOG
@@ -128,6 +130,8 @@ fi
 exit
 }
 
+MAKE_FLAGS=$@
+
 # build core and base plugins sequentially
 # exit if build fails (excluding checks)
 for m in $CORE; do