Beginning work on GN build

runtime/vm/BUILD.gn

Index: runtime/vm/BUILD.gn
diff --git a/runtime/vm/BUILD.gn b/runtime/vm/BUILD.gn
index f1c2da469a22a47e69d45326d966c4d821eae6da..7846baec0fc5513c123d3e4dd7675e61403778d3 100644
--- a/runtime/vm/BUILD.gn
+++ b/runtime/vm/BUILD.gn
@@ -43,17 +43,17 @@ static_library("libdart_platform") {
   ]
 }
 
+vm_sources_list = exec_script("../../tools/gypi_to_gn.py",
+                              [rebase_path("vm_sources.gypi")],
+                              "scope",
+                              ["vm_sources.gypi"])
+
 static_library("libdart_vm") {
   configs += ["..:dart_config",
               "..:dart_product_config",
               "..:dart_precompiled_runtime_config"]
   public_configs = [":libdart_vm_config"]
 
-  vm_sources_list = exec_script("../../tools/gypi_to_gn.py",
-                                [rebase_path("vm_sources.gypi")],
-                                "scope",
-                                ["vm_sources.gypi"])
-
   set_sources_assignment_filter(["*_test.cc", "*_test.h"])
   sources = vm_sources_list.sources
   include_dirs = [
@@ -68,10 +68,6 @@ static_library("libdart_vm_nosnapshot") {
               "..:dart_precompiled_runtime_config"]
   public_configs = [":libdart_vm_config"]
   defines = [ "DART_NO_SNAPSHOT" ]
-  vm_sources_list = exec_script("../../tools/gypi_to_gn.py",
-                                [rebase_path("vm_sources.gypi")],
-                                "scope",
-                                ["vm_sources.gypi"])
 
   set_sources_assignment_filter(["*_test.cc", "*_test.h"])
   sources = vm_sources_list.sources
@@ -87,10 +83,6 @@ static_library("libdart_vm_nosnapshot_with_precompiler") {
               "..:dart_precompiler_config"]
   public_configs = [":libdart_vm_config"]
   defines = [ "DART_NO_SNAPSHOT" ]
-  vm_sources_list = exec_script("../../tools/gypi_to_gn.py",
-                                [rebase_path("vm_sources.gypi")],
-                                "scope",
-                                ["vm_sources.gypi"])
 
   set_sources_assignment_filter(["*_test.cc", "*_test.h"])
   sources = vm_sources_list.sources