Fix incorrect string comparison in Firebase C++ SDK's CMakeLists.txt file.

Strings should be compared using `STREQUAL`, not `EQUAL`, because the latter expects the string to represent a number. Without the fix, the condition always fails and chooses `DEBUG`.

PiperOrigin-RevId: 285505285

Author: Googler

release_build_files/CMakeLists.txt

@@ -36,7 +36,7 @@ elseif(MSVC)
   else()
     set(MSVC_CPU x86)
   endif()
-  if(CMAKE_BUILD_TYPE EQUAL Release)
+  if(CMAKE_BUILD_TYPE STREQUAL Release)
     set(MSVC_CONFIG Release)
   else()
     set(MSVC_CONFIG Debug)