merge(3p/abseil_cpp): Merge upstream at 'ccdbb5941'

Change-Id: I6e85fc7b5f76bba1f1eef15e600a8acb64e97ef5

third_party/abseil_cpp/CMakeLists.txt

@@ -102,10 +102,8 @@ if(${ABSL_RUN_TESTS})
   # on the command line
   include(CTest)
   enable_testing()
-endif()
 
-## check targets
-if(BUILD_TESTING)
+  ## check targets
   if (NOT ABSL_USE_EXTERNAL_GOOGLETEST)
     set(absl_gtest_build_dir ${CMAKE_BINARY_DIR}/googletest-build)
     if(${ABSL_USE_GOOGLETEST_HEAD})
@@ -177,5 +175,7 @@ if(ABSL_ENABLE_INSTALL)
     FILES_MATCHING
       PATTERN "*.inc"
       PATTERN "*.h"
-  )
+      PATTERN "copts" EXCLUDE
+      PATTERN "testdata" EXCLUDE
+    )
 endif()  # ABSL_ENABLE_INSTALL