build: cmake: drop build_mode

there is no benefit having this variable. and it introduces
another layer of indirection. so drop it.

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

CMakeLists.txt

@@ -23,8 +23,7 @@ if(DEFINED CMAKE_BUILD_TYPE)
             "Following types are supported: ${scylla_build_types}")
     endif()
 endif(DEFINED CMAKE_BUILD_TYPE)
-string(TOUPPER "${CMAKE_BUILD_TYPE}" build_mode)
-include(mode.${build_mode})
+include(mode.${CMAKE_BUILD_TYPE})
 include(mode.common)
 add_compile_definitions(
     FMT_DEPRECATED_OSTREAM)

cql3/CMakeLists.txt

@@ -13,7 +13,7 @@ set(cql_parser_srcs ${cql_grammar_srcs})
 list(FILTER cql_parser_srcs INCLUDE REGEX "Parser.cpp$")
 
 set(unoptimized_levels "0" "g" "s")
-if(Seastar_OptimizationLevel_${build_mode} IN_LIST unoptimized_levels)
+if(Seastar_OptimizationLevel_${CMAKE_BUILD_TYPE} IN_LIST unoptimized_levels)
     # Unoptimized parsers end up using huge amounts of stack space and
     # overflowing their stack
     list(APPEND cql_parser_compile_options