[SR-14710] Building new driver as part of Swift compiler causes crash when using Swiftenv

[fwcd]

Previous ID	SR-14710
Radar	rdar://problem/78784575
Original Reporter	@fwcd
Type	Bug

Environment

Ubuntu 20.04, x86-64

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Project Infrastructure | |Labels | Bug | |Assignee | None | |Priority | Medium | md5: 465b98e5fe69eb8de62bf3513111e0c4

Issue Description:

~/git/swift-project/swift$ utils/build-script --release-debuginfo
 [utils/build-script] NOTE: Using toolchain default
 + cmake --version
 + mkdir -p /home/fw/git/swift-project/build/Ninja-RelWithDebInfoAssert
 — Building earlyswiftdriver —
 + /home/fw/git/swift-project/swift-driver/Utilities/build-script-helper.py build --package-path /home/fw/git/swift-project/swift-driver --build-path /home/fw/git/swift-project/build/Ninja-RelWithDebInfoAssert/earlyswiftdriver-linux-x86_64 --configuration release --toolchain /home/fw/.swiftenv --ninja-bin /usr/bin/ninja --cmake-bin /usr/bin/cmake --local_compiler_build
 — build-script-helper.py: error: [Errno 2] No such file or directory
 ERROR: command terminated with a non-zero exit status 1, aborting

Since Swiftenv provides Shims for binaries like swift (located at ~/.swiftenv/shims/swift), the build script helper seems to have trouble locating the toolchain home and uses ~/.swiftenv (whereas the actual toolchain is located at ~/.swiftenv/versions/VERSION).

[typesanitizer]

@swift-ci create