Remove rtc_use_lto GN arg.

This CL is a no-op since rtc_use_lto is always false and in general
such change should probably be implemented in
//build/config/compiler/BUILD.gn.

Bug: chromium:408997
Change-Id: Id37d3181e66e699f8cd535aee1af7609352a7259
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/149833
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28919}
diff --git a/common_audio/BUILD.gn b/common_audio/BUILD.gn
index 0dd5ec3..d8d4494 100644
--- a/common_audio/BUILD.gn
+++ b/common_audio/BUILD.gn
@@ -285,15 +285,6 @@
       cflags = [ "-mfpu=neon" ]
     }
 
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
-
     deps = [
       ":common_audio_neon_c",
       ":fir_filter",
@@ -318,15 +309,6 @@
       cflags = [ "-mfpu=neon" ]
     }
 
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
-
     deps = [
       ":common_audio_c",
       "../rtc_base:checks",
diff --git a/modules/audio_coding/BUILD.gn b/modules/audio_coding/BUILD.gn
index 1bfd7fb..e28964d 100644
--- a/modules/audio_coding/BUILD.gn
+++ b/modules/audio_coding/BUILD.gn
@@ -682,15 +682,6 @@
       cflags = [ "-mfpu=neon" ]
     }
 
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
-
     deps = [
       ":isac_fix_common",
       "../../common_audio",
diff --git a/modules/audio_processing/BUILD.gn b/modules/audio_processing/BUILD.gn
index eaa8826..e4df10b 100644
--- a/modules/audio_processing/BUILD.gn
+++ b/modules/audio_processing/BUILD.gn
@@ -348,15 +348,6 @@
       suppressed_configs += [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags = [ "-mfpu=neon" ]
     }
-
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
   }
 }
 
diff --git a/modules/audio_processing/aec/BUILD.gn b/modules/audio_processing/aec/BUILD.gn
index 294c43f..0deaba5 100644
--- a/modules/audio_processing/aec/BUILD.gn
+++ b/modules/audio_processing/aec/BUILD.gn
@@ -63,15 +63,6 @@
       cflags += [ "-mfpu=neon" ]
     }
 
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
-
     deps += [ "../../../common_audio" ]
   }
 
diff --git a/modules/audio_processing/aecm/BUILD.gn b/modules/audio_processing/aecm/BUILD.gn
index 8250173..dbb4d2f 100644
--- a/modules/audio_processing/aecm/BUILD.gn
+++ b/modules/audio_processing/aecm/BUILD.gn
@@ -34,15 +34,6 @@
       suppressed_configs += [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags += [ "-mfpu=neon" ]
     }
-
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
   }
 
   if (current_cpu == "mipsel") {
diff --git a/modules/audio_processing/agc/BUILD.gn b/modules/audio_processing/agc/BUILD.gn
index 09781b2..f8ed539 100644
--- a/modules/audio_processing/agc/BUILD.gn
+++ b/modules/audio_processing/agc/BUILD.gn
@@ -79,15 +79,6 @@
       suppressed_configs += [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags = [ "-mfpu=neon" ]
     }
-
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
   }
 }
 
diff --git a/modules/audio_processing/utility/BUILD.gn b/modules/audio_processing/utility/BUILD.gn
index b24d0e9..0ba0f5b 100644
--- a/modules/audio_processing/utility/BUILD.gn
+++ b/modules/audio_processing/utility/BUILD.gn
@@ -67,15 +67,6 @@
       suppressed_configs += [ "//build/config/compiler:compiler_arm_fpu" ]
       cflags += [ "-mfpu=neon" ]
     }
-
-    # Disable LTO on NEON targets due to compiler bug.
-    # TODO(fdegans): Enable this. See crbug.com/408997.
-    if (rtc_use_lto) {
-      cflags -= [
-        "-flto",
-        "-ffat-lto-objects",
-      ]
-    }
   }
 
   if (current_cpu == "mipsel" && mips_float_abi == "hard") {
diff --git a/webrtc.gni b/webrtc.gni
index dece36e..2e6ccc8 100644
--- a/webrtc.gni
+++ b/webrtc.gni
@@ -124,11 +124,6 @@
   # NDK r16 or above.
   rtc_enable_android_aaudio = false
 
-  # Link-Time Optimizations.
-  # Executes code generation at link-time instead of compile-time.
-  # https://gcc.gnu.org/wiki/LinkTimeOptimization
-  rtc_use_lto = false
-
   # Set to "func", "block", "edge" for coverage generation.
   # At unit test runtime set UBSAN_OPTIONS="coverage=1".
   # It is recommend to set include_examples=0.