external: add aarch64 submodules

openjdk.bin
gcc.bin
misc.bin

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
build: add gcc sysroot for cross builds

Cross-builds of shared objects need a libc to link against (even though it
won't be used at runtime) and startup files.  Provide them in the gcc.bin
external repository for cross builds.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
Update gcc.bin for glibc sysroot

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
build: relax naming of boost libraries

The aarch64 boost libraries have dropped the -mt suffix; so adapt the build
process to accept libraries with or without the suffix.  When the change
also arrives to x64 we can drop this hack.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>