[fuchsia] Move third_party/lss source location.

Fuchsia is unnesting third_party dependencies to be in a flat structure
in preperation for migrating to git submodules.

Bug: b/189352193
Change-Id: I603c40ea199a764145e509f02d5e3bce7925a77a
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/3179766
Commit-Queue: Francois Rousseau <frousseau@google.com>
Reviewed-by: Francois Rousseau <frousseau@google.com>
GitOrigin-RevId: 00b93a1772722bef23e1d873fab11979053df718
diff --git a/third_party/lss/BUILD.gn b/third_party/lss/BUILD.gn
index c0652cd..f104825 100644
--- a/third_party/lss/BUILD.gn
+++ b/third_party/lss/BUILD.gn
@@ -17,6 +17,8 @@
 config("lss_config") {
   if (crashpad_is_in_chromium) {
     defines = [ "CRASHPAD_LSS_SOURCE_EXTERNAL" ]
+  } else if (crashpad_is_in_fuchsia) {
+    defines = [ "CRASHPAD_LSS_SOURCE_FUCHSIA" ]
   } else {
     defines = [ "CRASHPAD_LSS_SOURCE_EMBEDDED" ]
   }
diff --git a/third_party/lss/lss.h b/third_party/lss/lss.h
index 11209ff..2646b6c 100644
--- a/third_party/lss/lss.h
+++ b/third_party/lss/lss.h
@@ -19,6 +19,8 @@
 #include "third_party/lss/linux_syscall_support.h"
 #elif defined(CRASHPAD_LSS_SOURCE_EMBEDDED)
 #include "third_party/lss/lss/linux_syscall_support.h"
+#elif defined(CRASHPAD_LSS_SOURCE_FUCHSIA)
+#include "../../../../third_party/lss/linux_syscall_support.h"
 #else
 #error Unknown lss source
 #endif