kbuild: call make once for all targets when O=.. is used

Change the invocations of make in the output directory Makefile and the main Makefile for separate object trees to pass all goals to one $(MAKE) via a new phony target "sub-make" and the existing target _all. When compiling with separate object directories, a separate make is called in the context of another directory (from the output directory the main Makefile is called, the Makefile is then restarted with current directory set to the object tree). Before this patch, when multiple make command goals are specified, each target results in a separate make invocation. With make -j, these invocations may run in parallel, resulting in multiple commands running in the same directory clobbering each others results. I did not try to address make -j for mixed dot-config and no-dot-config targets. Because the order does matter, a solution was not obvious. Perhaps a simple check for MAKEFLAGS having -j and refusing to run would be appropriate.

MMMilton Miller committed 19 years ago