Ensure meson's prefix is a valid absolute path

The path / is not considered an absolute path on Windows, failing with:

    ERROR: prefix value '/' must be an absolute path

os.path.abspath ensures that "/" becomes a valid absolute path on all major
platforms, resolving to "/" on Linux and macOS, and to "C:\" (or whichever
filesystem is currently active, could be E:\ as well) on Windows.

Closes #17204.

conan/tools/meson/meson.py

@@ -47,7 +47,7 @@ def configure(self, reconfigure=False):
                 cmd += f' --native-file "{native}"'
         cmd += ' "{}" "{}"'.format(build_folder, source_folder)
         # Issue related: https://github.com/mesonbuild/meson/issues/12880
-        cmd += ' --prefix=/'  # this must be an absolute path, otherwise, meson complains
+        cmd += f' --prefix={os.path.abspath("/")}'  # this must be an absolute path, otherwise, meson complains
         self._conanfile.output.info("Meson configure cmd: {}".format(cmd))
         self._conanfile.run(cmd)