Avoid resetting CC and GCC on Linuxbrew

Coupled with `--env=std` this allows pass through of a user's C compiler
environment on Linuxbrew with environmental variables. Avoids defaulting
to the system gcc/g++ which does not work on many module-based Linux
cluster distributions: Homebrew/linuxbrew#13
Add  flag to avoid isolating CC and GCC compiler choices as part of environment preparation.
Pass current CC/CXX environment to build with `--env=inherit`

This allows pass through of a user's C compiler environment on Linuxbrew
with environmental variables. Avoids defaulting to the system gcc/g++ which
does not work on many module-based Linux cluster distributions: Homebrew/linuxbrew#13
Clean up after rebase merge
Pass current CC/CXX environment to build with `--env=inherit`

This allows pass through of a user's C compiler environment on Linuxbrew
with environmental variables. Avoids defaulting to the system gcc/g++ which
does not work on many module-based Linux cluster distributions: Homebrew/linuxbrew#13
Clean up rebase
	new file:   Library/Formula/ldid.rb
	deleted:    Library/Formula/postgresql.rb
Merge branch 'linuxbrew' of https://github.com/sennychu/linuxbrew into linuxbrew

Conflicts:
	Library/Formula/postgresql.rb
	Library/Homebrew/extend/ENV.rb
	modified:   Library/Formula/lsyncd.rb
	modified:   Library/Homebrew/cmd/doctor.rb
	modified:   Library/Homebrew/extend/ENV.rb