Revert changes breaking build on FreeBSD (#7885)

* Add clang-versions used on modern FreeBSD versions.

This helps .NET build on FreeBSD.

* Update FreeBSD target

Current release is 12, not 11.

* Fix linking on FreeBSD.

These changes have previously been introduced in `dotnet/runtime`, but been reverted through automated updates later on.

This commit re-introduces them.

eng/common/cross/toolchain.cmake

@@ -44,7 +44,7 @@ elseif(TARGET_ARCH_NAME STREQUAL "x86")
   set(TOOLCHAIN "i686-linux-gnu")
 elseif (CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
   set(CMAKE_SYSTEM_PROCESSOR "x86_64")
-  set(triple "x86_64-unknown-freebsd11")
+  set(triple "x86_64-unknown-freebsd12")
 elseif (ILLUMOS)
   set(CMAKE_SYSTEM_PROCESSOR "x86_64")
   set(TOOLCHAIN "x86_64-illumos")
@@ -91,6 +91,9 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL "FreeBSD")
     set(CMAKE_CXX_COMPILER_TARGET ${triple})
     set(CMAKE_ASM_COMPILER_TARGET ${triple})
     set(CMAKE_SYSROOT "${CROSS_ROOTFS}")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fuse-ld=lld")
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -fuse-ld=lld")
+    set(CMAKE_MODULE_LINKER_FLAGS "${CMAKE_MODULE_LINKER_FLAGS} -fuse-ld=lld")
 elseif(ILLUMOS)
     set(CMAKE_SYSROOT "${CROSS_ROOTFS}")
 

eng/common/native/find-native-compiler.sh

@@ -55,7 +55,7 @@ if [ -z "$CLR_CC" ]; then
     # Set default versions
     if [ -z "$majorVersion" ]; then
         # note: gcc (all versions) and clang versions higher than 6 do not have minor version in file name, if it is zero.
-        if [ "$compiler" = "clang" ]; then versions=( 9 8 7 6.0 5.0 4.0 3.9 3.8 3.7 3.6 3.5 )
+        if [ "$compiler" = "clang" ]; then versions=( 12 11 10 9 8 7 6.0 5.0 4.0 3.9 3.8 3.7 3.6 3.5 )
         elif [ "$compiler" = "gcc" ]; then versions=( 9 8 7 6 5 4.9 ); fi
 
         for version in "${versions[@]}"; do