Rewrite assembler_test_base.h

Simplify the code in preparation of move to LLVM prebuilt tools.

Bug: 147817558
Test: m test-art-host-gtest
Change-Id: Iba277235255fd7d7f0965749b0b2d4a9567ced1f
diff --git a/compiler/utils/x86/assembler_x86_test.cc b/compiler/utils/x86/assembler_x86_test.cc
index baef254..d7bedd0 100644
--- a/compiler/utils/x86/assembler_x86_test.cc
+++ b/compiler/utils/x86/assembler_x86_test.cc
@@ -51,16 +51,8 @@
                              x86::Immediate>;
 
  protected:
-  std::string GetArchitectureString() override {
-    return "x86";
-  }
-
-  std::string GetAssemblerParameters() override {
-    return " --32";
-  }
-
-  std::string GetDisassembleParameters() override {
-    return " -D -bbinary -mi386 --no-show-raw-insn";
+  InstructionSet GetIsa() override {
+    return InstructionSet::kX86;
   }
 
   void SetUpHelpers() override {