Let `-test-all-packages` work with `-build-mode:test`

Fixes #3930

src/main.cpp

@@ -596,7 +596,7 @@ gb_internal bool parse_build_flags(Array<String> args) {
 	add_flag(&build_flags, BuildFlag_ObfuscateSourceCodeLocations, str_lit("obfuscate-source-code-locations"), BuildFlagParam_None,    Command__does_build);
 
 	add_flag(&build_flags, BuildFlag_Short,                   str_lit("short"),                     BuildFlagParam_None,    Command_doc);
-	add_flag(&build_flags, BuildFlag_AllPackages,             str_lit("all-packages"),              BuildFlagParam_None,    Command_doc | Command_test);
+	add_flag(&build_flags, BuildFlag_AllPackages,             str_lit("all-packages"),              BuildFlagParam_None,    Command_doc | Command_test | Command_build);
 	add_flag(&build_flags, BuildFlag_DocFormat,               str_lit("doc-format"),                BuildFlagParam_None,    Command_doc);
 
 	add_flag(&build_flags, BuildFlag_IgnoreWarnings,          str_lit("ignore-warnings"),           BuildFlagParam_None,    Command_all);
@@ -1733,6 +1733,12 @@ gb_internal bool parse_build_flags(Array<String> args) {
 		bad_flags = true;
 	}
 
+
+	if ((build_context.command_kind & (Command_doc | Command_test)) == 0 && build_context.test_all_packages) {
+		gb_printf_err("`-test-all-packages` can only be used with `odin build -build-mode:test`, `odin test`, or `odin doc`.\n");
+		bad_flags = true;
+	}
+
 	return !bad_flags;
 }