Strip i386 arch from tvOS compiler-rt lib (if present)

This is to avoid the following issue when generating toolchains for
macOS

```
ld: building for tvOS, but linking in object file built for tvOS
Simulator, file '/tmp/strip.mgCPcB' for architecture i386
fatal error:
/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/strip:
internal link edit command failed
```

This reverts commit 8470faf, #37929

Addresses rdar://80098850

Author: edymtt

utils/build-script-impl

@@ -1468,7 +1468,12 @@ function copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain() {
                 DEST_LIB_PATH="${DEST_BUILTINS_DIR}/${LIB_NAME}"
                 if [[ ! -f "${DEST_LIB_PATH}" ]]; then
                     if [[ -f "${HOST_LIB_PATH}" ]]; then
-                        call cp "${HOST_LIB_PATH}" "${DEST_LIB_PATH}"
+                        if [[ "$OS" == "tvos" ]]; then
+                            # This is to avoid strip failures when generating a toolchain
+                            call lipo -remove i386 "${HOST_LIB_PATH}" -output "${DEST_LIB_PATH}" || call cp "${HOST_LIB_PATH}" "${DEST_LIB_PATH}"
+                        else
+                           call cp "${HOST_LIB_PATH}" "${DEST_LIB_PATH}"
+                        fi
                     elif [[ "${VERBOSE_BUILD}" ]]; then
                         echo "no file exists at ${HOST_LIB_PATH}"
                     fi
@@ -1480,7 +1485,12 @@ function copy_embedded_compiler_rt_builtins_from_darwin_host_toolchain() {
                 DEST_SIM_LIB_PATH="${DEST_BUILTINS_DIR}/${SIM_LIB_NAME}"
                 if [[ ! -f "${DEST_SIM_LIB_PATH}" ]]; then
                     if [[ -f "${HOST_SIM_LIB_PATH}" ]]; then
-                        call cp "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}"
+                        if [[ "$OS" == "tvos" ]]; then
+                            # This is to avoid strip failures when generating a toolchain
+                            call lipo -remove i386 "${HOST_SIM_LIB_PATH}" -output "${DEST_SIM_LIB_PATH}" || call cp "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}"
+                        else
+                            call cp "${HOST_SIM_LIB_PATH}" "${DEST_SIM_LIB_PATH}"
+                        fi
                     elif [[ -f "${HOST_LIB_PATH}" ]]; then
                         # The simulator .a might not exist if the host
                         # Xcode is old. In that case, copy over the