meson: use better shellscript argument passing

Cherry-pick systemd commit ac3eda34[1] ("meson: use better shellscript
argument passing"):

    Passing potentially arbitrary data into a shellscript is potentially
    very broken if you do not correctly quote it for use. This quoting
    must be done as part of the interpretation of the data itself, e.g.
    python's shlex.quote; simply formatting it into a string with double
    quotes is NOT sufficient.

    An alternative is to communicate the data reliably via argv to the
    shell process, and allow the shell to internally handle it via
    `"$1"`, which is quote-safe and will expand the data from argv as a
    single tokenized word.

Also silences the following meson deprecation notice:

    NOTICE: Future-deprecated features used:
     * 0.55.0: {'ExternalProgram.path'}

[1]: systemd/systemd@ac3eda3

Author: cgzones

meson.build

@@ -109,8 +109,7 @@ gperf_test_format = '''
 const char * in_word_set(const char *, @0@);
 @1@
 '''
-gperf_snippet_format = 'echo foo,bar | @0@ -L ANSI-C'
-gperf_snippet = run_command('sh', '-c', gperf_snippet_format.format(gperf.path()), check: true)
+gperf_snippet = run_command('sh', '-c', 'echo foo,bar | "$1" -L ANSI-C', '_', gperf, check: true)
 gperf_test = gperf_test_format.format('size_t', gperf_snippet.stdout())
 if cc.compiles(gperf_test)
         gperf_len_type = 'size_t'