Clean up chatty 'echo' lines in llvm-link-wrapper.
Don't assume 'bash' will be at /bin/bash.
Teach llvm-link-wrapper to use LLVM_BUILD_DIR.

With soaap-ninja.diff and run-gyp in place, we no longer need to add LLVM to the current PATH in order to build Chrome, except for llvm-link-wrapper's PATH-dependence. This commit fixes that PATH-dependance: we prefer the llvm-link specified by LLVM_BUILD_DIR, but will use one from the PATH if that fails.
Drop more SOAAP-related $PATH munging.

Instead of requiring the 'soaap' binary to be on the $PATH, specify its location explicitly in Chromium's output build.ninja file.