Fixes for sanity-compiler-gcc and detection of linux variant

[Mike Duigou]

Hi all;

Two minor fixes for review:

6998014: Use /etc/lsb-release, when available, to detect linux variant and 
version
6998016: Incorrect ifdef nesting in sane-gcc-compiler rule

http://cr.openjdk.java.net/~mduigou/6998016.0/webrev/

Thanks!

Mike