wincodepage: minimize to indicate UTF-8 or not

The ANSI code page identifier is more information than generator
programs actually need.  The encoding of `build.ninja` is always
either UTF-8 or the system-wide ANSI code page.  Reduce the output
to provide no more information than the generator programs need.

The Console code page can be obtained in other ways, so drop it.

Author: bradking

doc/manual.asciidoc

@@ -308,17 +308,21 @@ file. _Available since Ninja 1.10._
 if they have one).  It can be used to know which rule name to pass to
 +ninja -t targets rule _name_+ or +ninja -t compdb+.
 
-`wincodepage`:: available on Windows hosts.  Prints the ANSI code page
-used by `ninja`, whose encoding is expected in `build.ninja`.  Also prints
-the Console code page for reference.  The output has the form:
+`wincodepage`:: Available on Windows hosts (_since Ninja 1.11_).
+Prints the Windows code page whose encoding is expected in the build file.
+The output has the form:
 +
 ----
-ANSI code page: %u
-Console code page: %u
+Build file encoding: <codepage>
 ----
 +
-where each `%u` is an integer code page identifier, expressed in decimal.
-_Available since Ninja 1.11._
+Additional lines may be added in future versions of Ninja.
++
+The `<codepage>` is one of:
+
+`UTF-8`::: Encode as UTF-8.
+
+`ANSI`::: Encode to the system-wide ANSI code page.
 
 Writing your own Ninja files
 ----------------------------

src/ninja.cc

@@ -648,8 +648,7 @@ int NinjaMain::ToolWinCodePage(const Options* options, int argc, char* argv[]) {
     printf("usage: ninja -t wincodepage\n");
     return 1;
   }
-  printf("ANSI code page: %u\n", GetACP());
-  printf("Console code page: %u\n", GetConsoleOutputCP());
+  printf("Build file encoding: %s\n", GetACP() == CP_UTF8? "UTF-8" : "ANSI");
   return 0;
 }
 #endif
@@ -1023,7 +1022,7 @@ const Tool* ChooseTool(const string& tool_name) {
     { "urtle", NULL,
       Tool::RUN_AFTER_FLAGS, &NinjaMain::ToolUrtle },
 #ifdef _WIN32
-    { "wincodepage", "print the Windows ANSI code page identifier",
+    { "wincodepage", "print the Windows code page used by ninja",
       Tool::RUN_AFTER_FLAGS, &NinjaMain::ToolWinCodePage },
 #endif
     { NULL, NULL, Tool::RUN_AFTER_FLAGS, NULL }