Revert "fix(build): remove duplicate rustflags"

This reverts commit 6cbf338.

The RUSTFLAGS in the .cargo/config.toml is used by language analyzers
to get the rust flags, so leave them here despite the redundancy.

Signed-off-by: Manish Vachharajani <[email protected]>

Author: mvachhar

.cargo/config.toml

@@ -7,6 +7,7 @@ PKG_CONFIG_PATH = { value = "compile-env/sysroot/x86_64-unknown-linux-gnu/releas
 [build]
 target = "x86_64-unknown-linux-gnu"
 rustc = "compile-env/bin/rustc"
+rustflags = ["--cfg", "tokio_unstable"]
 
 [target.x86_64-unknown-linux-gnu]
 runner = ["scripts/test-runner.sh"]