FindOpenSSL: Tolerate tabs in header while parsing version (#15765)

Tolerate tabs instead of spaces in the "# define" line.

Modules/FindOpenSSL.cmake

@@ -325,7 +325,7 @@ endfunction()
 if (OPENSSL_INCLUDE_DIR)
   if(OPENSSL_INCLUDE_DIR AND EXISTS "${OPENSSL_INCLUDE_DIR}/openssl/opensslv.h")
     file(STRINGS "${OPENSSL_INCLUDE_DIR}/openssl/opensslv.h" openssl_version_str
-         REGEX "^# *define[\t ]+OPENSSL_VERSION_NUMBER[\t ]+0x([0-9a-fA-F])+.*")
+         REGEX "^#[\t ]*define[\t ]+OPENSSL_VERSION_NUMBER[\t ]+0x([0-9a-fA-F])+.*")
 
     # The version number is encoded as 0xMNNFFPPS: major minor fix patch status
     # The status gives if this is a developer or prerelease and is ignored here.