This only enables the swift compiler (not its output) to be used with leaks
sanitizer on linux.
Some important notes: On Linux, right now we are not completely leak clean. I
was only able to get a -Onone build of the stdlib without triggering lsan (I was
unable to run the optimizer and the tests successfully). Additionally even at
-Onone, I had to suppress some leaks in the driver. The point of this though is
to prevent any further -Onone leaks from being committed to the tree since
-Onone leaks that are not bounded (unlike the driver bugs) could cause SourceKit
to leak memory. Since SourceKit is a long running process... such a type of leak
would be bad.
rdar://32876901
Why are the python reasons for having our code nested in a directory
called ``swift_build_support.swift_build_support/`` instead of simply
``swift_build_support/``? Is that what we really want here?
In a normal swiftless clang build, if it doesnt know CLANG_VERSION_*,
clang's cmake falls back on LLVM_VERSION_*. We pass a CLANG_COMPILER_VERSION
to swift, but it is not necessarily what clang wants to know.
The intention of this CLANG_VERSION_* flag in Clang is to know
what Swift calls clang_user_visible_version. This is the non-specific
version of Clang. For example, clang-900 - this is 9.0.0, while Swift
would like clang_compiler_version to be the specific version that the
driver will print out.
Flag naming!
Fix tests
Fix the mocked output files of swiftc. Change the lookup of
clang from build-script to build-script-impl like all the other
commands. Pass more args to LLVM. Fix swiftenv creation. Fix unit tests.
The reason this patch works is that build-script-impl gets
all the arguments that are not handled by build-script.
SR-237 calls for `build-script` and `build-script-impl` to be merged. This
commit takes another step towards that goal by moving the logic that finds
the path to the CMake executable up into `build-script`.
Users of `build-script` were previously able to specify which CMake
they wished to use via `build-script-impl` args, like so:
```
$ utils/build-script -- --cmake=/foo/bar/cmake
```
This commit preserves that behavior, while also allowing users to
specify that path via `build-script` args:
```
$ utils/build-script --cmake=/baz/cmake -- --other --flags
```
