Build SOS for Windows and Linux arm/arm64 architectures

[mikem8361]

• [x] dotnet-dump/SOSHost needs to support the ARM/ARM64 register set.
• [x] clrmd may need to be modified/built for linux arm/arm64 (clmd repo).
• [x] sos.dll on Windows needs to be built for arm and Linux libsos.dll need to be built for arm/arm64 (diagnostics repo).
• [x] sos.dll on Windows needs to load the cross platform long name DAC (diagnostics repo).
• [x] the Windows long name cross x86/arm DAC (mscordaccore_x86_arm_4.6.27617.04.dll) needs to be packaged in the runtime (coreclr repo).
• [x] the symbol uploader/downloader support (symstore and maybe dotnet-symuploader repos) need to be updated to handle the cross platform long name DAC.

[mikem8361]

It looks like the long name cross x86/arm DAC is already being added to the coreclr packages. All is needed is the changes to the symstore/symuploader to publish it to the servers.

[mikem8361]

All done now.