Work on GN iOS build.

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
-import("//build/config/sysroot.gni")
 if (cpu_arch == "arm") {
   import("//build/config/arm.gni")
 }
 
 # compiler ---------------------------------------------------------------------
 #
 # Base compiler configuration.
 #
 # See also "runtime_library" below for related stuff and a discusison about
 # where stuff should go. Put warning related stuff in the "warnings" config.
@@ skipping 39 matching lines @@
       cflags += [ "-fstack-protector-all" ]
     } else if (is_linux) {
       cflags += [ "-fstack-protector", "--param=ssp-buffer-size=4" ]
     }
   }
 
   # Mac-specific compiler flags setup.
   # ----------------------------------
   if (is_mac || is_ios) {
     # These flags are shared between the C compiler and linker.
-    common_mac_flags = [ "-isysroot", sysroot ]
-    if (is_mac) {
-      common_mac_flags += [ "-mmacosx-version-min=10.6" ]
-    } else {
-      cflags += [ "-mios-simulator-version-min=6.0" ]
-    }
+    common_mac_flags = []
 
     # CPU architecture.
     if (cpu_arch == "x64") {
       common_mac_flags += [ "-arch x86_64" ]
     } else if (cpu_arch == "x86") {
       common_mac_flags += [ "-arch i386" ]
     }
 
     cflags += common_mac_flags + [
       # Without this, the constructors and destructors of a C++ object inside
@@ skipping 86 matching lines @@
         # Experimentation found that using four linking threads
         # saved ~20% of link time.
         # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
         # Only apply this to the target linker, since the host
         # linker might not be gold, but isn't used much anyway.
         "-Wl,--threads",
         "-Wl,--thread-count=4",
       ]
     }
 
-    if (sysroot != "") {
-      cflags += [ "--sysroot=" + sysroot ]
-      ldflags += [ "--sysroot=" + sysroot ]
-
-      # Need to get some linker flags out of the sysroot.
-      ldflags += [ exec_script("../linux/sysroot_ld_path.py",
-          [rebase_path("../../linux/sysroot_ld_path.sh", ".", root_build_dir),
-           sysroot],
-          "value") ]
-    }
-
     ldflags += [
       "-fPIC",
       "-pthread",
       "-Wl,-z,noexecstack",
       "-Wl,-z,now",
       "-Wl,-z,relro",
     ]
   }
 
   # Clang-specific compiler flags setup.
@@ skipping 482 matching lines @@
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }