Using r2086 and I didn't see an open bug report for this.

Cross compiling for 64bit Windows is broken because of a missing file.  There should be a code/libs/win64/libcurl.a but it is missing in the SVN repository.

I'm able to compile for win32 fine because there is a code/libs/win32/libcurl.a.  It's only an issue with win64.

Building ioquake3 in build/release-mingw32-x64:
  PLATFORM: mingw32
  ARCH: x64
  VERSION: 1.36_SVN2086
  COMPILE_PLATFORM: linux
  COMPILE_ARCH: i386
  CC: x86_64-w64-mingw32-gcc
...
  CLIENT_LIBS:
    -lgdi32
    -lole32
    -lopengl32
    code/libs/win64/libcurl.a
    -lmingw32
    code/libs/win64/libSDLmain.a
    code/libs/win64/libSDL64.dll.a
...
WINDRES code/sys/win_resource.rc
CC code/sys/sys_win32.c
CC code/client/libmumblelink.c
CC code/sdl/sdl_glimp.c
LD build/release-mingw32-x64/ioquake3.x64.exe
x86_64-w64-mingw32-gcc: error: code/libs/win64/libcurl.a: No such file or directory
make[2]: *** [build/release-mingw32-x64/ioquake3.x64.exe] Error 1
make[2]: Leaving directory `/home/undead/ioquake3.git'
make[1]: *** [targets] Error 2
make[1]: Leaving directory `/home/undead/ioquake3.git'
make: *** [release] Error 2