package/ripgrep: add workaround for cargo bug #3349

To fix this bug we have to use an undocumented test variable to enable
the nightly target-applies-to-host feature so that the target linker
doesn't get used for host binaries like the build-script.

Fixes:
error: failed to run custom build command for `ripgrep v0.8.1 (/home/buildroot/buildroot/output/build/ripgrep-0.8.1)`

Caused by:
  process didn't exit successfully: `/home/buildroot/buildroot/output/build/ripgrep-0.8.1/target/release/build/ripgrep-59eeb7069534e1ef/build-script-build` (exit status: 1)
  --- stderr
  /home/buildroot/buildroot/output/build/ripgrep-0.8.1/target/release/build/ripgrep-59eeb7069534e1ef/build-script-build: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.33' not found (required by /home/buildroot/buildroot/output/build/ripgrep-0.8.1/target/release/build/ripgrep-59eeb7069534e1ef/build-script-build)

Details:
https://github.com/rust-lang/cargo/issues/3349
https://github.com/rust-lang/cargo/pull/9322



Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>