Make `SanitizerSafeCopy()` constexpr, and check for constant evaluati…

…on (#1399)

Also update test Docker container so that LTS patches can be tested

This patch cherry-picks 2 commits:
a0f9b46
35e8e3f

Apply LTS transformations for 20230125 LTS branch (#1370)

Apply LTS transformations for 20230125 LTS branch (#1370)

Switch time_state to explicit default initialization instead of value…

… initialization. (#1261)

It looks to me like the language rules treat these the same for this type, but evidently GCC feels differently.

This only matters under TSAN where SpinLock has a non-trivial destructor, and under C++20 where ABSL_CONST_INIT is implemented (as constinit) by gcc.

Fixes #1253

PiperOrigin-RevId: 469806751
Change-Id: Ic01b0142101f361bc19c95f9f9474e635669c58d

Apply LTS transformations for 20220623 LTS branch (#1202)

Apply LTS transformations for 20220623 LTS branch (#1202)

Fix Android build of elf_mem_image.cc (#1052)

Fix Android build of elf_mem_image.cc (#1052)

Abseil LTS 20210324, Patch 2

* Fixes build with glibc 2.34 (#952)
* Fixes "illegal thread local variable" on some Apple platforms (#954, #965)

Abseil LTS 20210324, Patch 1 (#943)

* Add missing `add_subdirectory()` call for "cleanup" (#925)

Since `absl::Cleanup` is now public, it should also be included
in the `absl/CMakeLists.txt` file.

Signed-off-by: Christian Blichmann <cblichmann@google.com>

* Correctly install pkgconfig files under CMAKE_INSTALL_LIBDIR
Fixes #931

PiperOrigin-RevId: 366816645

* AbseilConfigureCopts.cmake: fix AppleClang detection

restore use of MATCHES in comparison with "Clang"; this was lost in:

commit 22771d4
  ...
  24e1f5f72756046f5265abf618e951c341f09b8d by Derek Mauro <dmauro@google.com>:

  Fixes failing CMake string comparisons
  https://cmake.org/cmake/help/latest/policy/CMP0054.html

fixes:
CMake Warning at absl/copts/AbseilConfigureCopts.cmake:61 (message):
  Unknown compiler:
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++.
  Building with no default flags

Fixes #930

PiperOrigin-RevId: 366879337

* Increment SOVERSION to 2103.0.1

Co-authored-by: Christian Blichmann <cblichmann@users.noreply.github.com>
Co-authored-by: Abseil Team <absl-team@google.com>