internal/rosa: remove libcxxabi hack

This was caused by stack overflow which was resolved many commits ago.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/llvm.go

@@ -159,15 +159,6 @@ ln -s ld.lld /work/system/bin/ld
 			[2]string{"LIBCXX_HAS_MUSL_LIBC", "ON"},
 			[2]string{"LIBCXX_USE_COMPILER_RT", "ON"},
 		)
-
-		if t > toolchainStage0 {
-			// libcxxabi fails to compile if c++ headers not prefixed in /usr
-			// is found by the compiler, and doing this is easier than
-			// overriding CXXFLAGS; not using mv here to avoid chown failures
-			scriptEarly += `
-cp -r /system/include /usr/include && rm -rf /system/include
-`
-		}
 	}
 	if attr.flags&llvmRuntimeLibcxxABI != 0 {
 		cache = append(cache,