Improve handling of bundled ICU components

We are just installing a mode file.

gn.spec

@@ -52,15 +52,17 @@ Source2:        update-version
 #   https://src.fedoraproject.org/rpms/chromium/raw/
 #     ce30313f5e4af121140c037bf026453355534f24/f/
 #     chromium-84.0.4147.105-gn-gcc-cleanup.patch
-Patch0:         gn-39a87c0b-gcc-cleanup.patch
+Patch:          gn-39a87c0b-gcc-cleanup.patch
 # Stop overriding optimization flags
-Patch1:         gn-0153d369-no-O3.patch
+Patch:          gn-0153d369-no-O3.patch
 
-BuildRequires:  python3
 BuildRequires:  python3-devel
 BuildRequires:  ninja-build
 BuildRequires:  gcc-c++
 
+# For RPM macros:
+BuildRequires:  emacs-common
+
 %if %{with html_docs}
 BuildRequires:  pandoc
 BuildRequires:  parallel
@@ -71,10 +73,22 @@ Requires:       vim-filesystem
 Requires:       python3
 Provides:       vim-gn = %{version}-%{release}
 
-BuildRequires:  emacs
 Requires:       emacs-filesystem >= %{_emacs_version}
 Provides:       emacs-gn = %{version}-%{release}
 
+# src/base/third_party/icu/icu_utf.h:
+#
+#   This file has the relevant components from ICU copied to handle basic
+#   UTF8/16/32 conversions. Components are copied from umachine.h, utf.h,
+#   utf8.h, and utf16.h into icu_utf.h.
+#
+# The forked, bundled ICU components are copied from Chromium. Because of the
+# downstream changes (primarily, changing namespaces and symbol prefixes),
+# there is no clear path to unbundling.
+#
+# See src/base/third_party/icu/README.chromium, from which the version number
+# is taken.
+Provides:       bundled(icu) = 60
 
 %description
 GN is a meta-build system that generates build files for Ninja.
@@ -109,7 +123,7 @@ AR='gcc-ar'; export AR
 # Both --use-icf and --use-lto add compiler flags that only work with clang++,
 # not with g++. We do get LTO on Fedora anyway, since we respect the
 # distribution’s build flags.
-%{__python3} build/gen.py \
+%{python3} build/gen.py \
     --no-last-commit-position \
     --no-strip \
     --no-static-libstdc++
@@ -141,7 +155,7 @@ install -d '%{buildroot}%{_datadir}/vim/vimfiles'
 cp -vrp misc/vim/* '%{buildroot}%{_datadir}/vim/vimfiles'
 find '%{buildroot}%{_datadir}/vim/vimfiles' \
     -type f -name 'README.*' -print -delete
-%py_byte_compile %{__python3} '%{buildroot}%{_datadir}/vim/vimfiles/gn-format.py'
+%py_byte_compile %{python3} '%{buildroot}%{_datadir}/vim/vimfiles/gn-format.py'
 
 install -t '%{buildroot}%{_emacs_sitestartdir}' -D -p -m 0644 misc/emacs/*.el
 
@@ -176,7 +190,7 @@ grep -E '^#define[[:blank:]]+LAST_COMMIT_POSITION[[:blank:]]+'\
 
 
 %files doc
-%license LICENSE
+%license LICENSE src/base/third_party/icu/README.chromium
 %doc AUTHORS
 %doc OWNERS
 %doc README*.md