Add x64 arch and freebsd arm64 in cross toolchain

[am11]

Currently we recognize x64 architecture in cross toolchain for FreeBSD and illumos, but we do not treat it the same way as other architectures in the script. This PR moves x64 to the same plan as other architectures and adjusts the code flow.

Also added FreeBSD arm64.

[am11]

cc @sec, @Thefrank, @janvorli

This makes it easier to investigate issues like dotnet/runtime#71338 using docker on linux, mac or windows (without installing FreeBSD arm64). This script is used at https://github.com/dotnet/dotnet-buildtools-prereqs-docker/blob/main/src/ubuntu/18.04/cross/freebsd/12/hooks/pre-build to produce docker images for runtime build prerequisites.

[sec]

From my tests, isn't set(TOOLCHAIN "llvm") also needed here, as later eng/native/configuretools.cmake will fail while looking for objcopy ?

[am11]

TOOLCHAIN is used to indicate triplet for other platforms. For freebsd-x64, it should be the same value before and after this refactoring. The arm64 block is a copy of refactored x64 block.

[sec]

For compile to even start, I think that also lines:
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fuse-ld=lld")
should be
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fuse-ld=lld -stdlib=libc++ -Qunused-arguments")
so that llvm pickup the right library. Dunno if this is right variable, but without the second silence warning, it will fail some configure checks.

And also
if((TARGET_ARCH_NAME MATCHES "^(arm|armv6|armel|arm64|ppc64le|s390x)$" AND NOT ANDROID) OR ILLUMOS)
to
if((TARGET_ARCH_NAME MATCHES "^(arm|armv6|armel|arm64|ppc64le|s390x)$" AND NOT ANDROID AND NOT FREEBSD) OR ILLUMOS)
so that compiler targets are not overwritten, which will fail later.

thanks @am11 for starting this - as for docker images with arm64, I assume there will be a need for separate PR to add those Dockerfiles, right?

[Thefrank]

Just as a heads up from the readme.txt on FreeBSD's download FTP:

releases/${MACHINE}/${MACHINE_ARCH}/*-RELEASE/
    The official FreeBSD releases as individual tarballs to download; useful
    for jail hosting, updating machines in situ, etc.  Make sure to look in
    the ${MACHINE_ARCH} sub-directory for the most recent releases (e.g.,
    releases/amd64/amd64); this is a change from the earlier ${ARCH} naming
    scheme (e.g., releases/amd64).

so https://download.freebsd.org/ftp/releases/${__FreeBSDArch}/${__FreeBSDBase}/base.txz will work for now but might break in the future.

[janvorli]

I'm not sure if there's x64 Tizen. I have thought Tizen is only arm / x86. @alpencolt am I right?

[am11]

According to Wikipedia https://en.wikipedia.org/wiki/Tizen, x86-64 is supported. Here are the downloadable packages for x86_64: https://download.tizen.org/live/Tizen/standard/x86_64/

[am11]

@sec, thanks. I have updated the TOOLCHAIN related condition. As to the unused variable suppression, we can handle that in runtime/eng/native/configurecompiler.cmake etc. This toolchain.cmake is essentially to initialize variables in cross build scenario.

[sec]

What about a place to add -stdlib=libc++ -Qunused-arguments to that it won't fail with ld.lld: error: unable to find library -lstdc++ ?

[sec]

For the objcopy error, will this be ok?

diff --git a/eng/native/configuretools.cmake b/eng/native/configuretools.cmake
index 6697524c659..8476d82cca8 100644
--- a/eng/native/configuretools.cmake
+++ b/eng/native/configuretools.cmake
@@ -54,7 +54,11 @@ if(NOT WIN32 AND NOT CLR_CMAKE_TARGET_BROWSER)
       set(TOOLSET_PREFIX ${ANDROID_TOOLCHAIN_PREFIX})
     elseif(CMAKE_CROSSCOMPILING AND NOT DEFINED CLR_CROSS_COMPONENTS_BUILD AND
         CMAKE_SYSTEM_PROCESSOR MATCHES "^(armv8l|armv7l|armv6l|aarch64|arm|s390x|ppc64le)$")
-      set(TOOLSET_PREFIX "${TOOLCHAIN}-")
+        if(FREEBSD)
+         set(TOOLSET_PREFIX "llvm-")
+        else()
+         set(TOOLSET_PREFIX "${TOOLCHAIN}-")
+        endif()
     else()
       set(TOOLSET_PREFIX "")
     endif()

[am11]

objcopy configuration does not belong to toolchain.cmake. We set them in runtime/eng/native/configuretools.cmake. For more info on what "toolchain file" is for in cmake, see https://cmake.org/cmake/help/book/mastering-cmake/chapter/Cross%20Compiling%20With%20CMake.html#toolchain-files.

[am11]

as for docker images with arm64, I assume there will be a need for separate PR to add those Dockerfiles, right?

@sec, yes, we can add that after this PR is merged.

https://download.freebsd.org/ftp/releases/${__FreeBSDArch}/${__FreeBSDBase}/base.txz will work for now but might break in the future.

@Thefrank, thanks. Updated in 00dab08.

[janvorli]

LGTM, thank you!