[PATCH] D121871: [gn build] Use lld-link's new /winsysroot: flag

[Nico Weber via Phabricator via llvm-commits]

thakis created this revision.
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If `clang_base_path` is set, it must now point to a directory that contains
an lld-link built with D118070 <https://reviews.llvm.org/D118070>.

(If this is a problem for anyone, we can guard this behind a
lld_link_understands_winsysroot gn arg, but let's see if we can get away
without that for now.)

With this, it's possible to build everything in a normal cmd.exe Window,
an MSVC shell isn't needed \o/

(Assuming you set `clang_base_path`, and you set `sysroot` to a directory
that contains a win sysroot. If you have MSVC installed,
`python3 llvm\utils\sysroot.py make-fake --out-dir=my-sysroot` and
setting `sysroot = "//my-sysroot"` in args.gn works, for example.)


https://reviews.llvm.org/D121871

Files:
  llvm/utils/gn/build/BUILD.gn


Index: llvm/utils/gn/build/BUILD.gn
===================================================================
--- llvm/utils/gn/build/BUILD.gn
+++ llvm/utils/gn/build/BUILD.gn
@@ -297,6 +297,12 @@
     if (current_os == "win") {
       assert(is_clang, "sysroot only works with clang-cl as host compiler")
       cflags += [ "/winsysroot" + rebase_path(sysroot, root_build_dir) ]
+      if (use_lld) {
+        ldflags += [ "/winsysroot:" + rebase_path(sysroot, root_build_dir) ]
+
+        # FIXME: Remove once PR54409 is fixed.
+        ldflags += [ "/machine:x64" ]
+      }
     } else if (current_os != "ios" && current_os != "mac" &&
                current_os != "android") {
       cflags += [ "--sysroot=" + rebase_path(sysroot, root_build_dir) ]


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