X87: [turbofan] Add basic support for calling to (a subset of) C functions.

src/compiler/x87/linkage-x87.cc

Index: src/compiler/x87/linkage-x87.cc
diff --git a/src/compiler/x87/linkage-x87.cc b/src/compiler/x87/linkage-x87.cc
index ec702ccbf05b86f2937022261e564d519f88f6ab..e4606de4f29979f2e1ebeccd774a74838771829a 100644
--- a/src/compiler/x87/linkage-x87.cc
+++ b/src/compiler/x87/linkage-x87.cc
@@ -24,6 +24,7 @@ struct X87LinkageHelperTraits {
   }
   static Register CRegisterParameter(int i) { return no_reg; }
   static int CRegisterParametersLength() { return 0; }
+  static int CStackBackingStoreLength() { return 0; }
 };
 
 typedef LinkageHelper<X87LinkageHelperTraits> LH;