Prepare for |is_posix| switch in the Fuchsia build

|is_posix| will be switched to false for Fuchsia, this is a preliminary change.

Bug: chromium:812974
Change-Id: I3bfda3e056ad1e5229834286ce5d095d9204a428
Reviewed-on: https://webrtc-review.googlesource.com/65782
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#22753}
diff --git a/BUILD.gn b/BUILD.gn
index 32dc81d..edb033c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -120,7 +120,7 @@
       ".",
     ]
   }
-  if (is_posix) {
+  if (is_posix || is_fuchsia) {
     defines += [ "WEBRTC_POSIX" ]
   }
   if (is_ios) {
@@ -213,7 +213,7 @@
       "LOGGING_INSIDE_WEBRTC",
     ]
   } else {
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       # Enable more warnings: -Wextra is currently disabled in Chromium.
       cflags = [
         "-Wextra",
diff --git a/common_audio/BUILD.gn b/common_audio/BUILD.gn
index 6aee9d0..057b11c 100644
--- a/common_audio/BUILD.gn
+++ b/common_audio/BUILD.gn
@@ -303,7 +303,7 @@
       "resampler/sinc_resampler_sse.cc",
     ]
 
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       cflags = [ "-msse2" ]
     }
 
diff --git a/modules/audio_processing/BUILD.gn b/modules/audio_processing/BUILD.gn
index b0b4253..95761c3 100644
--- a/modules/audio_processing/BUILD.gn
+++ b/modules/audio_processing/BUILD.gn
@@ -394,7 +394,7 @@
       "utility/ooura_fft_sse2.cc",
       "utility/ooura_fft_tables_neon_sse2.h",
     ]
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       cflags += [ "-msse2" ]
     }
   }
diff --git a/modules/desktop_capture/BUILD.gn b/modules/desktop_capture/BUILD.gn
index 5a4383b..778d155 100644
--- a/modules/desktop_capture/BUILD.gn
+++ b/modules/desktop_capture/BUILD.gn
@@ -391,7 +391,7 @@
       "differ_vector_sse2.h",
     ]
 
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       cflags = [ "-msse2" ]
     }
   }
diff --git a/modules/video_processing/BUILD.gn b/modules/video_processing/BUILD.gn
index d0f995c..57673bd 100644
--- a/modules/video_processing/BUILD.gn
+++ b/modules/video_processing/BUILD.gn
@@ -78,7 +78,7 @@
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       cflags = [ "-msse2" ]
     }
   }
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 92088b0..80e4455 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -452,7 +452,7 @@
     libs += [ "log" ]
   }
 
-  if (is_posix) {
+  if (is_posix || is_fuchsia) {
     sources += [ "file_posix.cc" ]
   }
 
@@ -1019,7 +1019,7 @@
     defines += [ "_CRT_NONSTDC_NO_DEPRECATE" ]
   }
 
-  if (is_posix) {
+  if (is_posix || is_fuchsia) {
     sources += [
       "ifaddrs_converter.cc",
       "ifaddrs_converter.h",
@@ -1353,7 +1353,7 @@
         "win32window_unittest.cc",
       ]
     }
-    if (is_posix) {
+    if (is_posix || is_fuchsia) {
       sources += [
         "openssladapter_unittest.cc",
         "ssladapter_unittest.cc",