RFR: JDK-8136385: Various build speed improvements for windows

[Erik Joelsson]

Hello,

In the build-infra project, I have made various minor build speed 
improvements for Windows. These mostly affect incremental build 
performance, but in certain cases normal builds are also greatly 
affected. I find these worth committing to JDK 9 separately.

List of improvements:

* Rewrote DependOnVariable to use "-include" instead of $(shell $(CAT) 
...) to read the old variable value from the last make invocation. This 
has a pretty big impact on incremental build performance on Windows. 
Also started using the file function in make when available (in make 
4.0) instead of $(shell $(PRINTF) ...) when writing these files.

* Implemented ListPathsSafely using the file function when available. 
Since we require make 4.0 in cygwin, this will usually be the case when 
it matters.

* Reduced the number of shell execution in the compiler and link recipes 
by joining them together with "; \". When compiling a lot of native 
code, this tends to get quite expensive.

Bug: https://bugs.openjdk.java.net/browse/JDK-8136385
Webrev: http://cr.openjdk.java.net/~erikj/8136385/webrev.01/

/Erik