[gn] port f78f93b (libc++ tzdb)

Author: nico

llvm/utils/gn/secondary/libcxx/config.gni

@@ -4,4 +4,7 @@ declare_args() {
 
   # libc++ inline ABI namespace. Defaults to __n, where n is the ABI version.
   libcxx_abi_namespace = ""
+
+  # Build timezone database as part of libc++experimental.
+  libcxx_enable_time_zone_database = target_os == "linux"
 }

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -51,6 +51,11 @@ if (current_toolchain == default_toolchain) {
     } else {
       values += [ "_LIBCPP_ABI_NAMESPACE=__" + libcxx_abi_version ]
     }
+    if (!libcxx_enable_time_zone_database) {
+      values += [ "_LIBCPP_HAS_NO_TIME_ZONE_DATABASE=1" ]
+    } else {
+      values += [ "_LIBCPP_HAS_NO_TIME_ZONE_DATABASE=" ]
+    }
   }
 
   write_cmake_config("write_modulemap") {
@@ -351,6 +356,8 @@ if (current_toolchain == default_toolchain) {
       "__chrono/steady_clock.h",
       "__chrono/system_clock.h",
       "__chrono/time_point.h",
+      "__chrono/tzdb.h",
+      "__chrono/tzdb_list.h",
       "__chrono/weekday.h",
       "__chrono/year.h",
       "__chrono/year_month.h",

llvm/utils/gn/secondary/libcxx/src/BUILD.gn

@@ -12,7 +12,7 @@ declare_args() {
   # Build libc++ as a static library.
   libcxx_enable_static = true
 
-  # Build filesystem as part of libc++fs.a.
+  # Build filesystem as part of libc++.
   libcxx_enable_filesystem = target_os != "win"
 
   # Build libc++experimental.a.
@@ -307,6 +307,12 @@ if (libcxx_enable_experimental) {
     output_dir = runtimes_dir
     output_name = "c++experimental"
     sources = [ "experimental/memory_resource.cpp" ]
+    if (libcxx_enable_filesystem && libcxx_enable_time_zone_database) {
+      sources += [
+        "tz.cpp",
+        "tzdb_list.cpp",
+      ]
+    }
     deps = [ "//libcxx/include" ]
     configs += [ ":cxx_config" ]
     configs -= [