[gn] port 9d6b68b (libc++ tzdb to experimental/)

Author: nico

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

@@ -317,16 +317,16 @@ if (libcxx_enable_experimental) {
     sources = [ "experimental/keep.cpp" ]
     if (libcxx_enable_filesystem && libcxx_enable_time_zone_database) {
       sources += [
-        "include/tzdb/time_zone_private.h",
-        "include/tzdb/types_private.h",
-        "include/tzdb/tzdb_list_private.h",
-        "include/tzdb/tzdb_private.h",
+        "experimental/include/tzdb/time_zone_private.h",
+        "experimental/include/tzdb/types_private.h",
+        "experimental/include/tzdb/tzdb_list_private.h",
+        "experimental/include/tzdb/tzdb_private.h",
         # TODO TZDB The exception could be moved in chrono once the TZDB library
         # is no longer experimental.
-        "chrono_exception.cpp",
-        "time_zone.cpp",
-        "tzdb.cpp",
-        "tzdb_list.cpp",
+        "experimental/chrono_exception.cpp",
+        "experimental/time_zone.cpp",
+        "experimental/tzdb.cpp",
+        "experimental/tzdb_list.cpp",
       ]
     }
     deps = [ "//libcxx/include" ]