[5.8] LLVM product: amend installation path of compiler-rt libraries... (swiftlang#63312)

...copied from the host toolchain

Addresses swiftlang#62626, rdar://104724130

(cherry picked from commit e1b4137)

Author: edymtt

utils/swift_build_support/swift_build_support/products/llvm.py

@@ -459,6 +459,6 @@ def install(self, host_target):
 
         if self.args.llvm_install_components and system() == 'Darwin':
             clang_dest_dir = '{}{}'.format(host_install_destdir,
-                                           targets.install_prefix())
+                                           self.args.install_prefix)
             self.copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain(
                 clang_dest_dir)