Implement differently logic to strip and copy the tvos libraries

The previous logic could fail silently to copy the library if the i386
slice is not present in the first place (like it is the case for
`libclang_rt.tvos.a` in Xcode 13.0 beta 1) -- this will avoid errors
like

```
Undefined symbols for architecture arm64:
  "___isPlatformVersionAtLeast", referenced from:
    swift::initializeProtocolLookup() in ImageInspectionMachO.cpp.o
    swift::initializeProtocolConformanceLookup() in
ImageInspectionMachO.cpp.o
    swift::initializeTypeMetadataRecordLookup() in
ImageInspectionMachO.cpp.o
    swift::initializeDynamicReplacementLookup() in
ImageInspectionMachO.cpp.o
```

This is a backport of #38262

Addresses rdar://80209915

Author: edymtt

utils/build-script-impl

@@ -1423,6 +1423,25 @@ function cmake_config_opt() {
     fi
 }
 
+function copy_lib_stripping_architecture() {
+    local source="$1"
+    local dest="$2"
+    local arch="$3"
+
+    # An alternative approach would be to use || to first
+    # attempt the removal of the slice and fall back to the
+    # copy when failing.
+    # However, this would leave unneeded error messages in the logs
+    # that may hinder investigation; in addition, in this scenario
+    # the `call` function seems to not propagate correctly failure
+    # exit codes.
+    if lipo -archs "${source}" | grep -q "${arch}"; then
+        call lipo -remove "${arch}" "${source}" -output "${dest}"
+    else
+        call cp "${source}" "${dest}"
+    fi
+}
+
 function copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain() {
     local clang_dest_dir="$1"
 
@@ -1448,7 +1467,8 @@ function copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain() {
                 if [[ ! -f "${DEST_LIB_PATH}" ]]; then
                     if [[ -f "${HOST_LIB_PATH}" ]]; then
                         if [[ "$OS" == "tvos" ]]; then
-                            call lipo -remove i386 "${HOST_LIB_PATH}" -output "${DEST_LIB_PATH}" || call cp "${HOST_LIB_PATH}" "${DEST_LIB_PATH}"
+                            # This is to avoid strip failures when generating a toolchain
+                            copy_lib_stripping_architecture "${HOST_LIB_PATH}" "${DEST_LIB_PATH}" i386
                         else
                            call cp "${HOST_LIB_PATH}" "${DEST_LIB_PATH}"
                         fi
@@ -1464,7 +1484,8 @@ function copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain() {
                 if [[ ! -f "${DEST_SIM_LIB_PATH}" ]]; then
                     if [[ -f "${HOST_SIM_LIB_PATH}" ]]; then
                         if [[ "$OS" == "tvos" ]]; then
-                            call lipo -remove i386 "${HOST_SIM_LIB_PATH}" -output "${DEST_SIM_LIB_PATH}" || call cp "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}"
+                            # This is to avoid strip failures when generating a toolchain
+                            copy_lib_stripping_architecture "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}" i386
                         else
                             call cp "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}"
                         fi