Export of internal Abseil changes.

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fcf9d3facb12451964ad1850073cbfb6f9739379 by CJ Johnson <johnsoncj@google.com>:

Makes it obvious to readers that the comparison operators do not branch more than needed

PiperOrigin-RevId: 240811527

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680c586f81f805be68e96caffb28d5f46b6a6511 by Jon Cohen <cohenjon@google.com>:

Consistently use "if(" instead of "if (" in CMake files

PiperOrigin-RevId: 240621819

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c4acc506648622389f33f564fd94f8dda08cb61a by Tom Manshreck <shreck@google.com>:

Internal change

PiperOrigin-RevId: 240619556

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ddbc1894944aae96767c876a1ae8696ddaba42a2 by Jon Cohen <cohenjon@google.com>:

Remove the warning about install prefixes when we aren't installing abseil

PiperOrigin-RevId: 240614750

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086c4fad213d99e875038bc8a1c7268e28a7ebf3 by Abseil Team <absl-team@google.com>:

Adjust some tests and test cases which fail on WebAssembly

PiperOrigin-RevId: 240592367

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46c2c09723a37ef4911ae3c64aab92e3f0fdba79 by Abseil Team <absl-team@google.com>:

CMake install target update
- Add prefix absl_ to each target when install rule are disabled.
- Disable all install commands when absl is used as subdirectory (Fix #287)

PiperOrigin-RevId: 240575083

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8d88063ed5b16f982a91950693d37ca18fdd46d8 by Jon Cohen <cohenjon@google.com>:

Correctly link to Threads::Threads for a few cmake targets which were missing it.

PiperOrigin-RevId: 240574513
GitOrigin-RevId: fcf9d3facb12451964ad1850073cbfb6f9739379
Change-Id: I031c57de8cd88554348eb8bd1371d01d15ff1fc7

absl/base/internal/cmake_thread_test.cc

@@ -0,0 +1,22 @@
+// Copyright 2018 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <iostream>
+#include "absl/base/internal/thread_identity.h"
+
+int main() {
+  auto* tid = absl::base_internal::CurrentThreadIdentityIfPresent();
+  // Make sure the above call can't be optimized out
+  std::cout << (void*)tid << std::endl;
+}