deps: backport char16ptr.h to 57

[srl295]

• char16ptr.h is appended to the ICU 57 unistr.h
• this way, no v8 code change is needed.

Fixes: #19656

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[srl295]

note that #19624 is also needed

[srl295]

^ doesn't actually work (why did it seem to work locally?)… my 'floating patch' mechanism doesn't support header file patching.

[bnoordhuis]

For my curiosity: is there a reason we try to support old versions of ICU? It doesn't work when you try to link against the system ICU (logical) so it seems like the only use case is people downloading an old tarball manually and extracting that to deps/icu - but why would anyone do that?

[srl295]

Can test with:

configure --with-icu-source=https://ssl.icu-project.org/files/icu4c/57.1/icu4c-57_1-src.zip --download=all

@bnoordhuis good point… my point was for system-icu. But, floating patches against icu don't affect an icu that's already built and part of the system.

but why would anyone do that

The only benefit for doing "that" would be to verify compatibility (see #19657 ). But I think more importantly, the benefit of this PR is misguided: Fixing v8 would actually allow linking against the older system-icu.

[srl295]

#19710 actually solves the issue instead of hacking around it. The only benefit to this PR is that it fixes the floating patch mechanism to support patching header files (below). I'll close this for now.

diff --git a/configure b/configure
index df59b59e207..13fca229bf6 100755
--- a/configure
+++ b/configure
@@ -34,6 +34,8 @@ import shlex
 import subprocess
 import shutil
 import string
+import distutils
+from distutils import dir_util
 
 # If not run from node/, cd to node/.
 os.chdir(os.path.dirname(__file__) or '.')
@@ -1354,6 +1356,10 @@ def configure_intl(o):
     print('See the README.md.')
     # .. and we're not about to build it from .gyp!
     sys.exit(1)
+  # If we're not using the in-tree ICU, copy over any patched files
+  if with_icu_source and os.path.isdir('tools/icu/patches/%s' % icu_ver_major):
+    print('Copying ICU patches from tools/icu/patches/%s to %s' % (icu_ver_major, icu_full_path))
+    distutils.dir_util.copy_tree('tools/icu/patches/%s' % icu_ver_major, icu_full_path)
   # map from variable name to subdirs
   icu_src = {
     'stubdata': 'stubdata',