dependencies: Don't allow using the default binary for host on cross compiles

Otherwise we can end up finding dependencies from the build machine for
the host machine, which is incorrect. This alters cmake, pkg-config, and
all config-tool based dependencies.

Fixes: #7276

mesonbuild/cmake/executor.py

@@ -93,7 +93,7 @@ class CMakeExecutor:
             mlog.debug('CMake binary for %s is not cached' % self.for_machine)
             for potential_cmakebin in find_external_program(
                     environment, self.for_machine, 'cmake', 'CMake',
-                    environment.default_cmake):
+                    environment.default_cmake, allow_default_for_cross=False):
                 version_if_ok = self.check_cmake(potential_cmakebin)
                 if not version_if_ok:
                     continue

mesonbuild/dependencies/base.py

@@ -444,7 +444,7 @@ class ConfigToolDependency(ExternalDependency):
         best_match = (None, None)
         for potential_bin in find_external_program(
                 self.env, self.for_machine, self.tool_name,
-                self.tool_name, self.tools):
+                self.tool_name, self.tools, allow_default_for_cross=False):
             if not potential_bin.found():
                 continue
             tool = potential_bin.get_command()
@@ -568,9 +568,9 @@ class PkgConfigDependency(ExternalDependency):
         else:
             assert PkgConfigDependency.class_pkgbin[self.for_machine] is None
             mlog.debug('Pkg-config binary for %s is not cached.' % self.for_machine)
-            for potential_pkgbin in find_external_program(self.env, self.for_machine, 'pkgconfig', 'Pkg-config', environment.default_pkgconfig):
-                mlog.debug('Trying pkg-config binary {} for machine {} at {}'
-                           .format(potential_pkgbin.name, self.for_machine, potential_pkgbin.command))
+            for potential_pkgbin in find_external_program(
+                    self.env, self.for_machine, 'pkgconfig', 'Pkg-config',
+                    environment.default_pkgconfig, allow_default_for_cross=False):
                 version_if_ok = self.check_pkgconfig(potential_pkgbin)
                 if not version_if_ok:
                     continue