6875240: Reduce Makefile build time by limiting repeated exec's (mostly for cygwin building)
Current webrev: http://cr.openjdk.java.net/~ohair/openjdk7/jdk7-build-cygwin-6875240/webrev/ Effectively, these changes use the environment variables as a cache so that make variables are not repeatedly calculated, avoiding unnecessary fork/execs. My implementation requires a switch to GNU make 3.81. (My GNU make 3.81 binaries are at http://cr.openjdk.java.net/~ohair/MakeBinaries/) I measured a build on Solaris X86 just now, the fork system calls (forkx and vforkx) went from roughly 113,000 to 50,000. The build time on Solaris wasn't changed a lot, maybe shaved a few minutes off, but this should help with cygwin a great deal. No numbers on cygwin builds yet. -kto
