[CMake][Fuchsia] Include fewer targets in stage 1 build

[abrachet]

Summary

These targets are for cross compiling the stage 2 toolchain. But it is unlikely we will need a toolchain on ARM32 ever, or RISC-V in a very long time.

[phosek]

This won't work for the cross-compilation case where the stage 1 compiler is used to build stage 2 runtimes (since stage 2 compiler is cross-compiled and cannot be used on the host). We would need some other mechanism to handle that use case.

[abrachet]

In D123906#3457587, @phosek wrote:

This won't work for the cross-compilation case where the stage 1 compiler is used to build stage 2 runtimes (since stage 2 compiler is cross-compiled and cannot be used on the host). We would need some other mechanism to handle that use case.

Ah, I did not think about that case, thanks.

clang/cmake/caches/Fuchsia.cmake

 # This file sets up a CMakeCache for a Fuchsia toolchain build.
 
-set(LLVM_TARGETS_TO_BUILD X86;ARM;AArch64;RISCV CACHE STRING "")
+set(LLVM_TARGETS_TO_BUILD X86;AArch64 CACHE STRING "")
 
 set(PACKAGE_VENDOR Fuchsia CACHE STRING "")
 
 set(LLVM_ENABLE_PROJECTS "bolt;clang;clang-tools-extra;lld;llvm;polly" CACHE STRING "")
 
 set(LLVM_ENABLE_DIA_SDK OFF CACHE BOOL "")
 set(LLVM_ENABLE_LIBXML2 OFF CACHE BOOL "")
 set(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR ON CACHE BOOL "")