spa: switch the include header test to C++ by default

If we have a C++ compiler, compile all the #include tests with that - it'll
pick up any issues that a C compiler will pick up anyway. This saves us from
having a separate C++ compiler test and it'll test each header separately for
C++ compatibility..

spa/tests/gen-cpp-test.py

@@ -1,24 +0,0 @@
-#!/usr/bin/env python3
-#
-# Generates a simple .cpp file including all of the SPA headers.
-#
-# Usage: gen-cpp-test.py path/to/pipewire.git/spa/include/spa
-
-template = """
-@@INCLUDES@@
-
-int main(int argc, char *argv[])
-{
-    return 0;
-}
-"""
-
-import sys
-from pathlib import Path
-
-basedir = Path(sys.argv[1])
-includes = [
-    "#include <{}>".format(f.relative_to(basedir.parent)) for f in sorted(basedir.rglob("*.h"))
-]
-
-print(template.replace("@@INCLUDES@@", "\n".join(includes)))

spa/tests/meson.build

@@ -30,21 +30,9 @@ foreach a : test_apps
   endif
 endforeach
 
-if have_cpp
-  gen_cpp_test = find_program('gen-cpp-test.py')
-  src_test_cpp = custom_target('gen-cpp-test',
-                               command: [gen_cpp_test, meson.source_root() / 'spa' / 'include' / 'spa'],
-                               output: 'test-cpp.cpp',
-                               capture: true)
-  # compilation test only
-  executable('spa-test-cpp', src_test_cpp,
-             include_directories : [spa_inc ],
-             dependencies : [],
-             install : false)
-endif
-
 # Generate a compilation test for each SPA header, excluding the type-info.h
 # ones which have circular dependencies and take some effort to fix.
+# Do it for C++ if possible (picks up C++-specific errors), otherwise for C.
 find = find_program('find', required: false)
 if find.found()
   spa_headers = run_command(find_program('find'),
@@ -55,10 +43,11 @@ if find.found()
                             '-printf', '%P\n')
   foreach spa_header : spa_headers.stdout().split('\n')
     if spa_header.endswith('.h')  # skip empty lines
+      ext = have_cpp ? '.cpp' : '.c'
       c = configuration_data()
       c.set('INCLUDE', spa_header)
       src = configure_file(input: 'spa-include-test-template.c',
-                          output: 'spa-include-test-@0@.c'.format(spa_header.underscorify()),
+                          output: 'spa-include-test-@0@.@1@'.format(spa_header.underscorify(), ext),
                           configuration: c)
       executable('spa-include-test-@0@'.format(spa_header.underscorify()),
                  src,