qemu/osdep: Switch position of "extern" and "G_NORETURN"

qemu/osdep: Switch position of "extern" and "G_NORETURN"

Fixes the Windows build under msys2 using GCC 12 which fails with the following
error:

  [184/579] Compiling C++ object qga/vss-win32/qga-vss.dll.p/install.cpp.obj
  FAILED: qga/vss-win32/qga-vss.dll.p/install.cpp.obj
  "c++" "-m64" "-mcx16" "-Iqga/vss-win32/qga-vss.dll.p" "-Iqga/vss-win32" "-I../src/qga/vss-win32" "-I." "-Iqapi" "-Itrace" "-Iui" "-Iui/shader" "-IC:/msys64/mingw64/include/glib-2.0" "-IC:/msys64/mingw64/lib/glib-2.0/include" "-fdiagnostics-color=auto" "-Wall" "-Winvalid-pch" "-Wnon-virtual-dtor" "-Werror" "-std=gnu++11" "-g" "-iquote" "." "-iquote" "C:/msys64/home/shentey/Projects/qemu/src" "-iquote" "C:/msys64/home/shentey/Projects/qemu/src/include" "-iquote" "C:/msys64/home/shentey/Projects/qemu/src/tcg/i386" "-D__STDC_LIMIT_MACROS" "-D__STDC_CONSTANT_MACROS" "-D__STDC_FORMAT_MACROS" "-fno-pie" "-no-pie" "-D_GNU_SOURCE" "-D_FILE_OFFSET_BITS=64" "-D_LARGEFILE_SOURCE" "-fno-strict-aliasing" "-fno-common" "-fwrapv" "-Wundef" "-Wwrite-strings" "-Wtype-limits" "-Wformat-security" "-Wformat-y2k" "-Winit-self" "-Wignored-qualifiers" "-Wempty-body" "-Wendif-labels" "-Wexpansion-to-defined" "-Wimplicit-fallthrough=2" "-Wmissing-format-attribute" "-Wno-missing-include-dirs" "-Wno-shift-negative-value" "-Wno-psabi" "-fstack-protector-strong" "-Wno-unknown-pragmas" "-Wno-delete-non-virtual-dtor" "-Wno-non-virtual-dtor" -MD -MQ qga/vss-win32/qga-vss.dll.p/install.cpp.obj -MF "qga/vss-win32/qga-vss.dll.p/install.cpp.obj.d" -o qga/vss-win32/qga-vss.dll.p/install.cpp.obj "-c" ../src/qga/vss-win32/install.cpp
  In file included from C:/msys64/mingw64/lib/glib-2.0/include/glibconfig.h:9,
              from C:/msys64/mingw64/include/glib-2.0/glib/gtypes.h:34,
              from C:/msys64/mingw64/include/glib-2.0/glib/galloca.h:34,
              from C:/msys64/mingw64/include/glib-2.0/glib.h:32,
              from C:/msys64/home/shentey/Projects/qemu/src/include/glib-compat.h:32,
              from C:/msys64/home/shentey/Projects/qemu/src/include/qemu/osdep.h:144,
              from ../src/qga/vss-win32/install.cpp:13:
  C:/msys64/mingw64/include/glib-2.0/glib/gmacros.h:1075:21: error: standard attributes in middle of decl-specifiers
  1075 | # define G_NORETURN [[noreturn]]
        |                     ^
  C:/msys64/home/shentey/Projects/qemu/src/include/qemu/osdep.h:240:8: note: in expansion of macro 'G_NORETURN'
  240 | extern G_NORETURN
        |        ^~~~~~~~~~
  C:/msys64/mingw64/include/glib-2.0/glib/gmacros.h:1075:21: note: standard attributes must precede the decl-specifiers to apply to the declaration, or follow them to apply to the type
  1075 | # define G_NORETURN [[noreturn]]
        |                     ^
  C:/msys64/home/shentey/Projects/qemu/src/include/qemu/osdep.h:240:8: note: in expansion of macro 'G_NORETURN'
  240 | extern G_NORETURN
        |        ^~~~~~~~~~
  C:/msys64/mingw64/include/glib-2.0/glib/gmacros.h:1075:21: error: attribute ignored [-Werror=attributes]
  1075 | # define G_NORETURN [[noreturn]]
        |                     ^
  C:/msys64/home/shentey/Projects/qemu/src/include/qemu/osdep.h:240:8: note: in expansion of macro 'G_NORETURN'
  240 | extern G_NORETURN
        |        ^~~~~~~~~~
  C:/msys64/mingw64/include/glib-2.0/glib/gmacros.h:1075:21: note: an attribute that appertains to a type-specifier is ignored
  1075 | # define G_NORETURN [[noreturn]]
        |                     ^
  C:/msys64/home/shentey/Projects/qemu/src/include/qemu/osdep.h:240:8: note: in expansion of macro 'G_NORETURN'
  240 | extern G_NORETURN
        |        ^~~~~~~~~~
  cc1plus.exe: all warnings being treated as errors

Apparently it also fixes the compilation with Clang 15 (see
https://gitlab.com/qemu-project/qemu/-/issues/1541 ).

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1541
Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20230318185931.181659-1-shentey@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>