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/llvm-context/src/target_machine/mod.rs

@@ -29,7 +29,7 @@ impl TargetMachine {
 
     /// LLVM target features.
     pub const VM_FEATURES: &'static str =
-        "+e,+m,+a,+c,+zbb,+auipc-addi-fusion,+ld-add-fusion,+lui-addi-fusion,+xtheadcondmov";
+        "+e,+m,+a,+c,+zbb,+auipc-addi-fusion,+ld-add-fusion,+lui-addi-fusion,+xtheadcondmov,+relax";
 
     /// A shortcut constructor.
     /// A separate instance for every optimization level is created.