ninjabackend: detect_vs_dep_prefix doesn't correctly handle clang-cl cross compilation.

[dalecurtis]

Traceback (most recent call last):
  File "/d/code/meson/mesonbuild/mesonmain.py", line 127, in run
    return options.run_func(options)
  File "/d/code/meson/mesonbuild/msetup.py", line 240, in run
    app.generate()
  File "/d/code/meson/mesonbuild/msetup.py", line 158, in generate
    self._generate(env)
  File "/d/code/meson/mesonbuild/msetup.py", line 210, in _generate
    intr.backend.generate(intr)
  File "/d/code/meson/mesonbuild/backend/ninjabackend.py", line 292, in generate
    with self.detect_vs_dep_prefix(tempfilename) as outfile:
  File "/d/code/meson/mesonbuild/backend/ninjabackend.py", line 254, in detect_vs_dep_prefix
    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  File "/usr/lib/python3.6/subprocess.py", line 709, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.6/subprocess.py", line 1258, in _execute_child
    executable = os.fsencode(executable)
  File "/usr/lib/python3.6/os.py", line 800, in fsencode
    filename = fspath(filename)  # Does type-checking of `filename`.
TypeError: expected str, bytes or os.PathLike object, not list

Fixing this by changing:
pc = subprocess.Popen([compiler.get_exelist(),
to:
pc = subprocess.Popen([compiler.get_exelist()[0],

Resolves that issue, but then the regex used to figure out the prefix is wrong on Linux. I.e., it doesn't handle paths like:
b'Note: including file: /d/code/chrome/src/third_party/depot_tools/win_toolchain/vs_files/418b3076791776573a815eb298c8aa590307af63/win_sdk/Include/10.0.18362.0/ucrt/stdio.h'

ERROR: Could not determine vs dep dependency prefix string.

This can be resolved by changing the regex from:
matchre = re.compile(rb"^(.*\s)[a-zA-Z]:\\.*stdio.h$")
to:
matchre = re.compile(rb"^(.*\s)([a-zA-Z]:\\|\/).*stdio.h$")

[xparq]

I'm new to meson, just started trying it, and immediately got stuck with the

ERROR: Could not determine vs dep dependency prefix string.

issue, without doing any cross-compilation or anything nontrivial. Unfortunately, I can't tell if my case is related at all; Google sent me here, when looking for this error message, FWIW.

[barcharcraz]

I got this with just MSVC, and not clang-cl.

This caused failure to compiler glib from source for me.

[wolenetz]

In meson v0.53.1 The "Could not determine vs dep dependency prefix string." portion of the problem still exists, and can be resolved using the updated matchre in OP, above (#5639 (comment))