cmake: Fix error building without CMAKE_BUILD_TYPE being set (hyprwm#…

…3590)

* Fix error building without CMAKE_BUILD_TYPE being set

This resolves the error building without a CMAKE_BUILD_TYPE.
CMake Error at CMakeLists.txt:36 (string):                                                                                                                                                          
  string no output variable specified

* CMake: convert CMake's build type to meson build type

Fix error when the CMAKE_BUILD_TYPE variable isn't set & properly convert the build type to mesons build type.

CMakeLists.txt

@@ -33,7 +33,24 @@ add_subdirectory("subprojects/udis86")
 message(STATUS "Setting up wlroots")
 
 include(ExternalProject)
-string(TOLOWER ${CMAKE_BUILD_TYPE} BUILDTYPE_LOWER)
+
+if(CMAKE_BUILD_TYPE)
+    string(TOLOWER ${CMAKE_BUILD_TYPE} BUILDTYPE_LOWER)
+    if(BUILDTYPE_LOWER STREQUAL "release")
+        # Pass.
+    elseif(BUILDTYPE_LOWER STREQUAL "debug")
+        # Pass.
+    elseif(BUILDTYPE_LOWER STREQUAL "relwithdebinfo")
+        set(BUILDTYPE_LOWER "debugoptimized")
+    elseif(BUILDTYPE_LOWER STREQUAL "minsizerel")
+        set(BUILDTYPE_LOWER "minsize")
+    else()
+        set(BUILDTYPE_LOWER "release")
+    endif()
+else()
+    set(BUILDTYPE_LOWER "release")
+endif()
+
 ExternalProject_Add(
     wlroots
     PREFIX ${CMAKE_SOURCE_DIR}/subprojects/wlroots
@@ -230,4 +247,4 @@ protocol("unstable/text-input/text-input-unstable-v1.xml" "text-input-unstable-v
 protocol("staging/cursor-shape/cursor-shape-v1.xml" "cursor-shape-v1" false)
 
 # hyprctl
-add_subdirectory(hyprctl)
+add_subdirectory(hyprctl)