Config changes to support target_os="fuchsia"

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index b05a8d746d8c5f0e2b9c84c2b3a16754672e65ef..7f6d1a311b6aed15222aaadc165c688f8032e1cc 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -169,6 +169,8 @@ config("compiler") {
     configs += [ "//build/config/mac:compiler" ]
   } else if (is_ios) {
     configs += [ "//build/config/ios:compiler" ]
+  } else if (is_fuchsia) {
+    configs += [ "//build/config/fuchsia:compiler" ]
   } else if (current_os == "aix") {
     configs += [ "//build/config/aix:compiler" ]
   }
@@ -309,7 +311,7 @@ config("compiler") {
 
   # Linux/Android common flags setup.
   # ---------------------------------
-  if (is_linux || is_android) {
+  if (is_linux || is_android || is_fuchsia) {
     if (use_pic) {
       cflags += [ "-fPIC" ]
       ldflags += [ "-fPIC" ]
@@ -339,7 +341,11 @@ config("compiler") {
           "-lpthread",
         ]
       }
-      ldflags += [ "-Wl,--as-needed" ]
+      if (!is_fuchsia) {

[jamesr1, 2017/05/11 22:00:32]

we can wrap just -lmxio with this, i.e.

ldflags += [ "-Wl,--as-needed", "-lmxio", "-Wl,--no-as-needed" ]

in the "compiler" config

+        # We need mxio/magenta to get linked in, even if they're not directly
+        # referenced.

[Nico, 2017/05/11 15:03:16]

Could you just add -l flags for those instead, to not lose --as-needed for
everything?

[scottmg, 2017/05/11 16:36:10]

Probably, yeah. Maybe what I'll do in this CL is just remove this, then in a
future CL that actually links something, it can add what it needs.

+        ldflags += [ "-Wl,--as-needed" ]
+      }
     }
   }