Fix build on musl.

Patch-Source: https://github.com/void-linux/void-packages/blob/master/srcpkgs/spotify-qt/patches/disable-crash-handler.patch

--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -26,13 +26,6 @@
 # Version macros
 target_compile_definitions(spotify-qt-lib PUBLIC LIB_VERSION="v${PROJECT_VERSION}")

-# Check if using GCC
-if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
-	# Used by crash handler
-	target_compile_definitions(spotify-qt-lib PRIVATE IS_GNU_CXX)
-	# Enable all compiler warnings
-	target_compile_options(spotify-qt-lib PRIVATE -Wall -Wextra)
-endif ()

 # Link optional libraries
 if (LIB_QT_LIBRARIES)