gn build: Make a couple of improvements to the unix toolchain.

[pcc]

Summary

Add an asm tool (will be required for building sanitizer_common on
x64) and set a soname for DSOs so that anything that links against
them gets the correct DT_NEEDED.

[phosek]

llvm/utils/gn/build/toolchain/BUILD.gn

44

This also needs {{asmflags}}.

[pcc]

• Address review comments

[pcc]

llvm/utils/gn/build/toolchain/BUILD.gn

44

Yes, also noticed that the description was wrong, fixed that too.

[phosek]

LGTM

llvm/utils/gn/build/toolchain/BUILD.gn

tool("cxx") {
       command = "$cxx -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} $target_cflags"
       depsformat = "gcc"
       description = "CXX {{output}}"
       outputs = [
         "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
       ]
     }
 
+    tool("asm") {
+      depfile = "{{output}}.d"
+      command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} $target_cflags"
+      depsformat = "gcc"
+      description = "CXX {{output}}"
+      outputs = [
+        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
+      ]
+    }
+
     tool("alink") {
       if (current_os == "mac") {
         command = "libtool -static -no_warning_for_no_symbols {{arflags}} -o {{output}} {{inputs}}"
       } else {
         # Remove the output file first so that ar doesn't try to modify the
         # existing file.
         command =
             "rm -f {{output}} && $ar rcsDT {{arflags}} {{output}} {{inputs}}"
       }
       description = "AR {{output}}"
       outputs = [
         "{{output_dir}}/{{target_output_name}}.a",
       ]
       output_prefix = "lib"
       default_output_dir = "{{root_out_dir}}/lib"
     }
 
     tool("solink") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "mac") {
         command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".dylib"
       } else {
-        command = "$ld -shared {{ldflags}} -Wl,-z,defs -o $outfile {{libs}} {{inputs}} $target_ldflags"
+        command = "$ld -shared {{ldflags}} -Wl,-z,defs -Wl,-soname,{{target_output_name}}{{output_extension}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".so"
       }
       description = "SOLINK $outfile"
       outputs = [
         outfile,
       ]
       lib_switch = "-l"
       output_prefix = "lib"
       default_output_dir = "{{root_out_dir}}/lib"
     }
 
     tool("solink_module") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "mac") {
         command = "$ld -shared {{ldflags}} -Wl,-flat_namespace -Wl,-undefined,suppress -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".dylib"
       } else {
-        command = "$ld -shared {{ldflags}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
+        command = "$ld -shared {{ldflags}} -Wl,-soname,{{target_output_name}}{{output_extension}} -o $outfile {{libs}} {{inputs}} $target_ldflags"
         default_output_extension = ".so"
       }
       description = "SOLINK $outfile"
       outputs = [
         outfile,
       ]
       lib_switch = "-l"
       default_output_dir = "{{root_out_dir}}/lib"