[lldb] Fix warnings

This patch fixes:

  lldb/unittests/ABI/AArch64/ABIAArch64Test.cpp:53:67: error: missing
  field 'value_regs' initializer
  [-Werror,-Wmissing-field-initializers]

  third-party/unittest/googletest/include/gtest/gtest.h:1379:11:
  error: comparison of integers of different signs: 'const unsigned
  long' and 'const int' [-Werror,-Wsign-compare]

Author: kazutakahirata

lldb/unittests/ABI/AArch64/ABIAArch64Test.cpp

@@ -50,12 +50,15 @@ TEST_P(ABIAArch64TestFixture, AugmentRegisterInfo) {
   ASSERT_TRUE(abi_sp);
   using Register = DynamicRegisterInfo::Register;
 
-  Register pc{ConstString("pc"), ConstString(), ConstString("GPR")};
+  Register pc;
+  pc.name = ConstString("pc");
+  pc.alt_name = ConstString();
+  pc.set_name = ConstString("GPR");
   std::vector<Register> regs{pc};
 
   abi_sp->AugmentRegisterInfo(regs);
 
-  ASSERT_EQ(regs.size(), 1);
+  ASSERT_EQ(regs.size(), 1U);
   Register new_pc = regs[0];
   EXPECT_EQ(new_pc.name, pc.name);
   EXPECT_EQ(new_pc.set_name, pc.set_name);