python-pyflame: Limit support to just glibc based systems
Fixes:
| checking build system type... x86_64-pc-linux-gnu
| checking host system type... x86_64-bec-linux-musl
| configure: error: Pyflame can only be built for Linux hosts
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Andrew Jeffery <andrew@aj.id.au>