Reland "Add WebRTC specific dcheck_always_on."

This is a reland of 9f2a20f4342a3e86e1f9fdfe6f3d76fb539d41c2

See https://webrtc-review.googlesource.com/c/src/+/226563/1..2
for the fix. RTC_DCHECK_ALWAYS_ON needs to be in public_configs
in order to be propagated together with header #includes and
avoid ODR violations.

Original change's description:
> Add WebRTC specific dcheck_always_on.
>
> Inspired by V8 CL: crrev.com/c/3038528.
>
> This makes the WebRTC's dcheck control independent of Chromium's and
> prepares switching Chromium's default behavior without affecting
> WebRTC developers or builders.
>
> Preparation for: https://crrev.com/c/2893204
>
> Bug: chromium:1225701, webrtc:12988
> Change-Id: Ia0d21f9fb8e9d7704fd1beca16504c301a263b3b
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226465
> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
> Reviewed-by: Markus Handell <handellm@webrtc.org>
> Reviewed-by: Dirk Pranke <dpranke@google.com>
> Cr-Commit-Position: refs/heads/master@{#34512}

Bug: chromium:1225701, webrtc:12988
Change-Id: I1f78587487ee7b1a4a07b8c91b737a9e797b2323
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226563
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34519}
diff --git a/tools_webrtc/coverage/generate_ios_coverage_command.py b/tools_webrtc/coverage/generate_ios_coverage_command.py
index e01a75c..ff17c58 100644
--- a/tools_webrtc/coverage/generate_ios_coverage_command.py
+++ b/tools_webrtc/coverage/generate_ios_coverage_command.py
@@ -89,7 +89,7 @@
     target_cpu = 'x64' if is_simulator else 'arm64'
     return ([] + ['target_os="ios"'] + ['target_cpu="%s"' % target_cpu] +
             ['use_clang_coverage=true'] + ['is_component_build=false'] +
-            ['dcheck_always_on=true'])
+            ['rtc_dcheck_always_on=true'])
 
 
 def GenerateIOSSimulatorCommand():
@@ -103,7 +103,7 @@
                     [FormatIossimTest(t, is_xctest=True) for t in XC_TESTS] +
                     [FormatIossimTest(t, is_xctest=False) for t in TESTS])
 
-    print 'To get code coverage using iOS simulator just run following commands:'
+    print 'To get code coverage using iOS sim just run following commands:'
     print ''
     print ' '.join(gn_cmd)
     print ''