Tests: Tests failure on Windows as a result of `PkgConfigParser` issues

[bkhouri]

Some PkgConfigParserTests fail on Windows as a result of the PkgConfigParser.parse() failing to parse the *.pc file in some circumstances.

Test Suite 'Selected tests' started at 2025-05-05 10:15:07.763
Test Suite 'PkgConfigParserTests' started at 2025-05-05 10:15:07.767
Test Case 'PkgConfigParserTests.testCircularPCFile' started at 2025-05-05 10:15:07.767
<EXPR>:0: error: PkgConfigParserTests.testCircularPCFile : threw error "parsing error(s): Expected a value for variable 'libdir' in C:\source\Tests\PackageLoadingTests\pkgconfigInputs\harfbuzz.pc. Variables: ["pcfiledir": "C:\\source\\Test
s\\PackageLoadingTests\\pkgconfigInputs", "pc_sysrootdir": "\\"]"
Test Case 'PkgConfigParserTests.testCircularPCFile' failed (0.021 seconds)
Test Suite 'PkgConfigParserTests' failed at 2025-05-05 10:15:07.788
         Executed 1 test, with 1 failure (1 unexpected) in 0.021 (0.021) seconds
Test Suite 'Selected tests' failed at 2025-05-05 10:15:07.788
         Executed 1 test, with 1 failure (1 unexpected) in 0.021 (0.021) seconds

The failures are observed in the self-hosted CI pipelines, but was not observed on host.

[dschaefer2]

This is very much a hand rolled parser. I'll double check it handles Windows newlines and backslash path separators properly.