[llgo] build llgoi by default

[axw]

Summary

As llgoi is installed, it must be built or the install
target will fail; there is no implicit dependency.
Adding llgoi to "ALL" makes building llgo as part of an
entire LLVM distribution a bit friendlier: you can then
just do the typical "make && make install".

[pcc]

LGTM

CMakeLists.txt

GOFLAGS "cc=${CMAKE_BINARY_DIR}/bin/clang"
           "go=${CMAKE_BINARY_DIR}/bin/llgo-go"
           "llgo=${CMAKE_BINARY_DIR}/bin/llgo-stage2${CMAKE_EXECUTABLE_SUFFIX}"
 )
 
 llvm_add_go_executable(cc-wrapper llvm.org/llgo/cmd/cc-wrapper DEPENDS
   cmd/cc-wrapper/main.go
 )
 
-llvm_add_go_executable(llgoi llvm.org/llgo/cmd/llgoi
+llvm_add_go_executable(llgoi llvm.org/llgo/cmd/llgoi ALL
   DEPENDS libgo ${CMAKE_BINARY_DIR}/bin/llgo${CMAKE_EXECUTABLE_SUFFIX}
           ${CMAKE_BINARY_DIR}/lib/go/llgo-${LLGO_VERSION}/cgo
           ${CMAKE_BINARY_DIR}/bin/llgo-go${CMAKE_EXECUTABLE_SUFFIX}
           cmd/llgoi/llgoi.go
   GOFLAGS "cc=${CMAKE_BINARY_DIR}/bin/clang"
           "cxx=${CMAKE_BINARY_DIR}/bin/clang++"
           "go=${CMAKE_BINARY_DIR}/bin/llgo-go"
 )