[Linux] Enable frame pointers when building Swift libraries.

[al45tair]

Turn on frame pointers for the Swift runtime libraries. This makes backtraces that go through the runtimes more reliable without having to parse DWARF data.

rdar://116112040

[al45tair]

@swift-ci Please test

[al45tair]

Explanation: Set -fno-omit-frame-pointer when building the Swift runtime libraries.
Original PR: #68986
Reviewed by: @mikeash
Resolves: rdar://116112040
Tests: Adds a test that checks that we get a decent backtrace when someone calls fatalError().

[al45tair]

@swift-ci Please test

[shahmishal]

lit.py: /home/build-user/llvm-project/llvm/utils/lit/lit/TestingConfig.py:138: fatal: unable to parse config file '/home/build-user/swift/test/lit.cfg', traceback: Traceback (most recent call last):
  File "/home/build-user/llvm-project/llvm/utils/lit/lit/TestingConfig.py", line 127, in load_from_path
    exec(compile(data, path, 'exec'), cfg_globals, None)
  File "/home/build-user/swift/test/lit.cfg", line 585, in <module>
    config.substitutions.append( ('%swift-host-lib-dir', config.swift_host_lib_dir))
AttributeError: 'TestingConfig' object has no attribute 'swift_host_lib_dir'

[al45tair]

That doesn't seem to be something I've changed.

[al45tair]

Yeah, that's #68858. It deleted

config.swift_host_lib_dir = make_path(config.swift_lib_dir, 'swift', 'host')

but didn't remove

config.substitutions.append( ('%swift-host-lib-dir', config.swift_host_lib_dir))

[al45tair]

@swift-ci Please test