Add Windows ARM 64-bit base tools (#376)

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This change is a part of
#305 feature work.

The change expanded the accepted target architecture for VS builds with
`AARCH64` option, which will output native Windows ARM64 binaries.

Note that the warnings due to integer conversions are suppressed for
this specific target to avoid too much local changes carried in MU. The
formal change should drop all these binaries and move to pythonic
scripts.

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`[x]`.
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- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
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- [ ] Impacts security?
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    flow, or firmware?
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    validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
    in build or boot behavior?
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    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
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    outside direct code modifications (and comments)?
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This was tested on Windows ARM64 hardware systems.

N/A

BaseTools/Source/C/Makefiles/ms.common

@@ -52,13 +52,23 @@ LIB_PATH     = $(BASE_TOOLS_PATH)\Lib\Win64
 SYS_BIN_PATH = $(EDK_TOOLS_PATH)\Bin\Win64
 SYS_LIB_PATH = $(EDK_TOOLS_PATH)\Lib\Win64
 
-# MU_CHANGE Starts: Adding support to build base tools for ARM
+# MU_CHANGE Starts: Adding support to build base tools for ARM and AARCH64
 !ELSEIF "$(HOST_ARCH)"=="ARM"
 ARCH_INCLUDE = $(EDK2_PATH)\MdePkg\Include\Arm
 BIN_PATH     = $(BASE_TOOLS_PATH)\Bin\Win32
 LIB_PATH     = $(BASE_TOOLS_PATH)\Lib\Win32
 SYS_BIN_PATH = $(EDK_TOOLS_PATH)\Bin\Win32
 SYS_LIB_PATH = $(EDK_TOOLS_PATH)\Lib\Win32
+!ELSEIF "$(HOST_ARCH)"=="AARCH64"
+ARCH_INCLUDE = $(EDK2_PATH)\MdePkg\Include\AArch64
+BIN_PATH     = $(BASE_TOOLS_PATH)\Bin\Win64
+LIB_PATH     = $(BASE_TOOLS_PATH)\Lib\Win64
+SYS_BIN_PATH = $(EDK_TOOLS_PATH)\Bin\Win64
+SYS_LIB_PATH = $(EDK_TOOLS_PATH)\Lib\Win64
+# Note: These are bit-width conversion related warning suppressions we carry to avoid much more
+#       overrides in the C code. The future plan is to replace all of these binary based tools
+#       with python scripts, when it happens in tianocore..
+CFLAGS = $(CFLAGS) /wd4267 /wd4244 /wd4334
 # MU_CHANGE Ends
 
 !ELSE