Makefile: add new DEFAULT_MAX_JOBS variable

Makefile

@@ -2,13 +2,15 @@
 # See index.html for further information.
 
 MXE_TARGETS        := i686-pc-mingw32
+DEFAULT_MAX_JOBS   := 6
 SOURCEFORGE_MIRROR := freefr.dl.sourceforge.net
 PKG_MIRROR         := s3.amazonaws.com/mxe-pkg
 PKG_CDN            := d1yihgixbnrglp.cloudfront.net
 
 PWD        := $(shell pwd)
 SHELL      := bash
-JOBS       := $(shell nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 1)
+NPROCS     := $(shell nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 1)
+JOBS       := $(shell printf "$(DEFAULT_MAX_JOBS)\n$(NPROCS)" | sort -n | head -1)
 
 INSTALL    := $(shell ginstall --help >/dev/null 2>&1 && echo g)install
 LIBTOOL    := $(shell glibtool --help >/dev/null 2>&1 && echo g)libtool