cmake: Set CMAKE_BUILD_TYPE before adjusting config-specific flags

This is a move-only change and required for the following commit.

CMakeLists.txt

@@ -167,6 +167,29 @@ option(SECP256K1_BUILD_EXHAUSTIVE_TESTS "Build exhaustive tests." ON)
 option(SECP256K1_BUILD_CTIME_TESTS "Build constant-time tests." ${SECP256K1_VALGRIND})
 option(SECP256K1_BUILD_EXAMPLES "Build examples." OFF)
 
+# Set the default build configuration.
+if(PROJECT_IS_TOP_LEVEL)
+  get_property(is_multi_config GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
+  set(default_build_type "RelWithDebInfo")
+  if(is_multi_config)
+    set(CMAKE_CONFIGURATION_TYPES "${default_build_type}" "Release" "Debug" "MinSizeRel" "Coverage" CACHE STRING
+      "Supported configuration types."
+      FORCE
+    )
+  else()
+    set_property(CACHE CMAKE_BUILD_TYPE PROPERTY
+      STRINGS "${default_build_type}" "Release" "Debug" "MinSizeRel" "Coverage"
+    )
+    if(NOT CMAKE_BUILD_TYPE)
+      message(STATUS "Setting build type to \"${default_build_type}\" as none was specified")
+      set(CMAKE_BUILD_TYPE "${default_build_type}" CACHE STRING
+        "Choose the type of build."
+        FORCE
+      )
+    endif()
+  endif()
+endif()
+
 # Redefine configuration flags.
 # We leave assertions on, because they are only used in the examples, and we want them always on there.
 if(MSVC)
@@ -200,28 +223,6 @@ mark_as_advanced(
   CMAKE_SHARED_LINKER_FLAGS_COVERAGE
 )
 
-if(PROJECT_IS_TOP_LEVEL)
-  get_property(is_multi_config GLOBAL PROPERTY GENERATOR_IS_MULTI_CONFIG)
-  set(default_build_type "RelWithDebInfo")
-  if(is_multi_config)
-    set(CMAKE_CONFIGURATION_TYPES "${default_build_type}" "Release" "Debug" "MinSizeRel" "Coverage" CACHE STRING
-      "Supported configuration types."
-      FORCE
-    )
-  else()
-    set_property(CACHE CMAKE_BUILD_TYPE PROPERTY
-      STRINGS "${default_build_type}" "Release" "Debug" "MinSizeRel" "Coverage"
-    )
-    if(NOT CMAKE_BUILD_TYPE)
-      message(STATUS "Setting build type to \"${default_build_type}\" as none was specified")
-      set(CMAKE_BUILD_TYPE "${default_build_type}" CACHE STRING
-        "Choose the type of build."
-        FORCE
-      )
-    endif()
-  endif()
-endif()
-
 include(TryAppendCFlags)
 if(MSVC)
   # Keep the following commands ordered lexicographically.