RISCV relaxations (#408)

This PR enables RISC-V relaxations and changes to internal linkage for internal function and global symbols.

See also:
https://github.com/llvm/llvm-project/issues/167381#issuecomment-3513830043

Signed-off-by: xermicus <cyrill@parity.io>

crates/linker/src/elf.rs

@@ -78,7 +78,7 @@ SECTIONS {
             "--error-limit=0",
             "--relocatable",
             "--emit-relocs",
-            "--no-relax",
+            "--relax",
             "--unique",
             "--gc-sections",
             self.linker_script_path.to_str().expect("should be utf8"),