Reland "[build] disable C++ optimization for mksnapshot code."

This is a reland of cee2f772

Original change's description:
> [build] disable C++ optimization for mksnapshot code.
> 
> By disabling C++ optimizations for code that's only run in mksnapshot,
> that is, CSA and Torque-generated code, we can save compile time.
> I observed up to 2x improvements of compile time for some files,
> while the mksnapshot time did not increase significantly.
> 
> Bug: v8:7629
> Change-Id: I96be2966611b2471b68023e0dd9e351d94f0013c
> Reviewed-on: https://chromium-review.googlesource.com/c/1460941
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59585}

Bug: v8:7629
Change-Id: I8330f93173ab3d7b400e15ea4935bbe8256b250f
Reviewed-on: https://chromium-review.googlesource.com/c/1473292
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59606}

BUILD.gn

@@ -670,6 +670,32 @@ config("toolchain") {
   }
 }
 
+config("default_optimization") {
+  if (is_debug && !v8_optimized_debug) {
+    configs = [ "//build/config/compiler:no_optimize" ]
+  } else {
+    # TODO(crbug.com/621335) Rework this so that we don't have the confusion
+    # between "optimize_speed" and "optimize_max".
+    if (((is_posix && !is_android) || is_fuchsia) && !using_sanitizer) {
+      configs = [ "//build/config/compiler:optimize_speed" ]
+    } else {
+      configs = [ "//build/config/compiler:optimize_max" ]
+    }
+  }
+}
+
+# For code that is only run a few times during the build, C++ optimizations
+# are a waste of time.
+config("unoptimized_initializer") {
+  configs = [ ":internal_config" ]
+  if (is_ubsan) {
+    # UBSan doesn't work without optimizations.
+    configs += [ ":default_optimization" ]
+  } else {
+    configs += [ "//build/config/compiler:no_optimize" ]
+  }
+}
+
 # Configs for code coverage with gcov. Separate configs for cflags and ldflags
 # to selectively influde cflags in non-test targets only.
 config("v8_gcov_coverage_cflags") {
@@ -984,7 +1010,8 @@ v8_source_set("torque_generated_initializers") {
     ]
   }
 
-  configs = [ ":internal_config" ]
+  remove_configs = [ v8_path_prefix + ":default_optimization" ]
+  configs = [ ":unoptimized_initializer" ]
 }
 
 action("generate_bytecode_builtins_list") {
@@ -1460,7 +1487,8 @@ v8_source_set("v8_initializers") {
     sources -= [ "src/builtins/builtins-intl-gen.cc" ]
   }
 
-  configs = [ ":internal_config" ]
+  remove_configs = [ v8_path_prefix + ":default_optimization" ]
+  configs = [ ":unoptimized_initializer" ]
 }
 
 v8_source_set("v8_init") {

gni/v8.gni

@@ -94,20 +94,8 @@ v8_add_configs = [
   v8_path_prefix + ":toolchain",
 ]
 
-if (is_debug && !v8_optimized_debug) {
-  v8_remove_configs += [ "//build/config/compiler:default_optimization" ]
-  v8_add_configs += [ "//build/config/compiler:no_optimize" ]
-} else {
-  v8_remove_configs += [ "//build/config/compiler:default_optimization" ]
-
-  # TODO(crbug.com/621335) Rework this so that we don't have the confusion
-  # between "optimize_speed" and "optimize_max".
-  if (((is_posix && !is_android) || is_fuchsia) && !using_sanitizer) {
-    v8_add_configs += [ "//build/config/compiler:optimize_speed" ]
-  } else {
-    v8_add_configs += [ "//build/config/compiler:optimize_max" ]
-  }
-}
+v8_remove_configs += [ "//build/config/compiler:default_optimization" ]
+v8_add_configs += [ v8_path_prefix + ":default_optimization" ]
 
 if (v8_code_coverage && !is_clang) {
   v8_add_configs += [
@@ -149,21 +137,21 @@ template("v8_source_set") {
                              "configs",
                              "remove_configs",
                            ])
+    configs -= v8_remove_configs
+    configs += v8_add_configs
     if (defined(invoker.remove_configs)) {
       configs -= invoker.remove_configs
     }
     configs += invoker.configs
-    configs -= v8_remove_configs
-    configs += v8_add_configs
   }
 }
 
 template("v8_header_set") {
   jumbo_source_set(target_name) {
     forward_variables_from(invoker, "*", [ "configs" ])
-    configs += invoker.configs
     configs -= v8_remove_configs
     configs += v8_add_configs
+    configs += invoker.configs
   }
 }
 
@@ -175,12 +163,12 @@ template("v8_executable") {
                              "configs",
                              "remove_configs",
                            ])
+    configs -= v8_remove_configs
+    configs += v8_add_configs
     if (defined(invoker.remove_configs)) {
       configs -= invoker.remove_configs
     }
     configs += invoker.configs
-    configs -= v8_remove_configs
-    configs += v8_add_configs
     if (is_linux) {
       # For enabling ASLR.
       ldflags = [ "-pie" ]
@@ -203,9 +191,9 @@ template("v8_executable") {
 template("v8_component") {
   component(target_name) {
     forward_variables_from(invoker, "*", [ "configs" ])
-    configs += invoker.configs
     configs -= v8_remove_configs
     configs += v8_add_configs
+    configs += invoker.configs
   }
 }
 
@@ -213,9 +201,9 @@ template("v8_static_library") {
   static_library(target_name) {
     complete_static_lib = true
     forward_variables_from(invoker, "*", [ "configs" ])
-    configs += invoker.configs
     configs -= v8_remove_configs
     configs -= [ "//build/config/compiler:thin_archive" ]
     configs += v8_add_configs
+    configs += invoker.configs
   }
 }