Add comments to the toolchain files

cmake/flags-gcc-x86_64.cmake

@@ -1,3 +1,19 @@
+#
+# 86Box     A hypervisor and IBM PC system emulator that specializes in
+#           running old operating systems and software designed for IBM
+#           PC systems and compatibles from 1981 through fairly recent
+#           system designs based on the PCI bus.
+#
+#           This file is part of the 86Box distribution.
+#
+#           CMake toolchain file defining GCC compiler flags
+#           for 64-bit x86 targets.
+#
+# Authors:  David Hrdlička, <hrdlickadavid@outlook.com>
+#
+#           Copyright 2021 David Hrdlička.
+#
+
 include(${CMAKE_CURRENT_LIST_DIR}/flags-gcc.cmake)
 
 set(CMAKE_C_FLAGS_INIT      "-m64 -march=x86-64 -msse2 -mfpmath=sse ${CMAKE_C_FLAGS_INIT}")