Remove unused importer package.
Fix a mistake in the instructions and document more clearly the required dependencies
Merge pull request #204 from pcc/cleanup

Remove unused importer package.
Merge pull request #205 from pcc/readme

Fix a mistake in the instructions and document more clearly the required...
Overhaul bootstrap.sh script:

- Initial support for build variants (e.g., LTO, sanitizers).
- Build libgo deps from bootstrap script. We will need to do this for
  build variants.
- Filter everything from libgo's make output except package names. This
  makes the output much easier to read.
Add support for LTO and sanitizer variants to the driver and bootstrap script

None of these work correctly at the moment without workdir hackery, so they
are not built by default. Furthermore, most of the sanitizer variants either
fail to build or run correctly.

Of the sanitizers, TSan seems to work best (although that isn't saying much),
and while it does not appear to be able to detect races between goroutines
running in the same thread, I've managed to provoke it into detecting a race
between goroutines running in different threads by creating a large number
of goroutines and setting GOMAXPROCS to a large value.

It also found a number of potential data races in libgo itself, but these
need more investigation.

It might initially seem pointless to support ASan and MSan, but they could
be useful for finding bugs in libgo, and bugs arising from interaction with
libraries written in other languages.
Pass -isystem to gcc

Also clarify what we use gcc for.
Merge pull request #207 from pcc/isystem

Pass -isystem to gcc
Merge pull request #206 from pcc/variants

Add support for LTO and sanitizer variants to the driver and bootstrap script
Make the clang update stamp depend on the LLVM revision in gollvm
Use llvm.Version to determine the correct resource path
Merge pull request #208 from pcc/updstamp

Make the clang update stamp depend on the LLVM revision in gollvm
Merge pull request #209 from pcc/version

Use llvm.Version to determine the correct resource path
Update for LLVM API change
Merge pull request #210 from pcc/roll

Update for LLVM API change
Roll libbacktrace to r210256

This incorporates a bug fix for large binaries with lots of debug info.
Debug info: Do not create files with empty names

This works around a bug in cgo which sometimes causes it to use the //line
directive with an empty file name.
Add test output files to .gitignore
Merge pull request #211 from pcc/roll-libbacktrace

Roll libbacktrace to r210256
Merge pull request #212 from pcc/debuginfo

Debug info: Do not create files with empty names