From: Benjamin Barenblat <bbaren@google.com>
Subject: Use libatomic if necessary
Bug-Debian: https://bugs.debian.org/973492

On some architectures, notably armel, Abseil needs symbols defined in
libatomic. Abseil does not currently have a well-developed system to
declare external library dependencies, so just have the linker determine
if anything needs libatomic and add the DT_NEEDED entry where necessary.

--- a/absl/copts/AbseilConfigureCopts.cmake
+++ b/absl/copts/AbseilConfigureCopts.cmake
@@ -64,4 +64,8 @@
   set(ABSL_TEST_COPTS "")
 endif()
 
+list(APPEND ABSL_DEFAULT_LINKOPTS
+    "-Wl,--as-needed" "-latomic" "-Wl,--no-as-needed"
+)
+
 set(ABSL_CXX_STANDARD "${CMAKE_CXX_STANDARD}")