[yugabyte#7994]: docdb: Fixed clang 10.* version detection

Summary:
Commit yugabyte@306d57f added thread safety improvements in the Transaction class and disabled thread-safety annotations/analysis for clang versions prior to 11. But clang version was incorrectly detected if reported as `Apple LLVM version 10.0.1 (clang-1001.0.46.4)`. Therefore, for such compiler versions, thread-safety annotations were enabled and causing compilation failures, because thread safety analysis does not work well with unique_lock prior to clang 11.

Fixed apple clang version detection in this case.

Test Plan: Jenkins, check logs and make sure the version of apple clang was reported as `Apple LLVM version 10.*`, detected correctly as `10.*` and compilation has been successfully completed.

Reviewers: dmitry, mbautin, bogdan

Reviewed By: bogdan

Subscribers: ybase

Differential Revision: https://phabricator.dev.yugabyte.com/D11215

cmake_modules/CompilerInfo.cmake

@@ -76,6 +76,9 @@ elseif("${COMPILER_VERSION_FULL}" MATCHES ".*clang-700\\..*")
   set(COMPILER_VERSION "3.7.0svn")
 
 # a different version of clang
+elseif("${COMPILER_VERSION_FULL}" MATCHES "Apple LLVM version ([0-9]+([.][0-9]+)*) .*")
+  set(COMPILER_FAMILY "clang")
+  set(COMPILER_VERSION "${CMAKE_MATCH_1}")
 elseif("${COMPILER_VERSION_FULL}" MATCHES ".*[(]clang-[0-9.]+[)].*")
   set(COMPILER_FAMILY "clang")
   string(REGEX REPLACE ".*[(]clang-([0-9.]+)[)].*" "\\1"