* make: add new target `gen-cov-report`

* ci: test with openlibm-test

* ci: checkout openlibm first

* ci: set OPENLIBM_HOME

* ci: update repo name

The recent addition of aarch64 fenv support uses BSD-specific types
(__uint64_t and __uint32_t) that are not defined on Linux systems,
causing compilation failures on aarch64-linux targets.

This commit replaces BSD-specific types with standard C99 types:
- __uint64_t → uint64_t
- __uint32_t → uint32_t

These standard types are available on all platforms through the
included <stdint.h> header.

Additionally, this fixes the initialization of __fe_dfl_env from
scalar 0 to {0} to match the typedef as a non-scalar type.

Fixes build failures on aarch64-linux-gnu and other non-BSD platforms.