Add GN builds on loongarch platform.

Currently, chromium has merged loongarch config file in bug:1454442,
and so we resubmit gn builds support for loongarch.

Bug: chromium:1289502
Change-Id: Iac83f5ea016945f7d9cc5f6de20d4c561bab6347
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/4615589
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>

BUILD.gn

@@ -36,6 +36,12 @@ config("libyuv_config") {
   if (libyuv_disable_rvv) {
     defines += [ "LIBYUV_DISABLE_RVV" ]
   }
+  if (!libyuv_use_lsx) {
+    defines += [ "LIBYUV_DISABLE_LSX" ]
+  }
+  if (!libyuv_use_lasx) {
+    defines += [ "LIBYUV_DISABLE_LASX" ]
+  }
 }
 
 # This target is built when no specific target is specified on the command line.
@@ -74,6 +80,14 @@ group("libyuv") {
     deps += [ ":libyuv_msa" ]
   }
 
+  if (libyuv_use_lsx) {
+    deps += [ ":libyuv_lsx"]
+  }
+
+  if (libyuv_use_lasx) {
+    deps += [ ":libyuv_lasx"]
+  }
+
   if (!is_ios && !libyuv_disable_jpeg) {
     # Make sure that clients of libyuv link with libjpeg. This can't go in
     # libyuv_internal because in Windows x64 builds that will generate a clang
@@ -236,6 +250,44 @@ if (libyuv_use_msa) {
   }
 }
 
+if (libyuv_use_lsx) {
+  static_library("libyuv_lsx") {
+    sources = [
+      # LSX Source Files
+      "source/row_lsx.cc",
+      "source/rotate_lsx.cc",
+      "source/scale_lsx.cc",
+    ]
+
+    cflags_cc = [
+      "-mlsx",
+      "-Wno-c++11-narrowing",
+    ]
+
+    deps = [ ":libyuv_internal" ]
+
+    public_configs = [ ":libyuv_config" ]
+  }
+}
+
+if (libyuv_use_lasx) {
+  static_library("libyuv_lasx") {
+    sources = [
+      # LASX Source Files
+      "source/row_lasx.cc",
+    ]
+
+    cflags_cc = [
+      "-mlasx",
+      "-Wno-c++11-narrowing",
+    ]
+
+    deps = [ ":libyuv_internal" ]
+
+    public_configs = [ ":libyuv_config" ]
+  }
+}
+
 if (libyuv_include_tests) {
   config("libyuv_unittest_warnings_config") {
     if (!is_win) {

libyuv.gni

@@ -7,6 +7,7 @@
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/arm.gni")
+import("//build/config/loongarch64.gni")
 import("//build/config/mips.gni")
 import("//build_overrides/build.gni")
 
@@ -21,4 +22,8 @@ declare_args() {
       (current_cpu == "mips64el" || current_cpu == "mipsel") && mips_use_msa
   libyuv_use_mmi =
       (current_cpu == "mips64el" || current_cpu == "mipsel") && mips_use_mmi
+  libyuv_use_lsx =
+      (current_cpu == "loong64") && loongarch64_use_lsx
+  libyuv_use_lasx =
+      (current_cpu == "loong64") && loongarch64_use_lasx
 }