[llvm] Use StringRef::{starts,ends}_with (NFC)

This patch replaces uses of StringRef::{starts,ends}with with
StringRef::{starts,ends}_with for consistency with
std::{string,string_view}::{starts,ends}_with in C++20.

I'm planning to deprecate and eventually remove
StringRef::{starts,ends}with.

llvm/lib/TargetParser/Host.cpp

@@ -1536,7 +1536,7 @@ StringRef sys::detail::getHostCPUNameForSPARC(StringRef ProcCpuinfoContent) {
   // Look for cpu line to determine cpu name
   StringRef Cpu;
   for (unsigned I = 0, E = Lines.size(); I != E; ++I) {
-    if (Lines[I].startswith("cpu")) {
+    if (Lines[I].starts_with("cpu")) {
       Cpu = Lines[I].substr(5).ltrim("\t :");
       break;
     }
@@ -1853,7 +1853,7 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
 
   // Look for the CPU features.
   for (unsigned I = 0, E = Lines.size(); I != E; ++I)
-    if (Lines[I].startswith("Features")) {
+    if (Lines[I].starts_with("Features")) {
       Lines[I].split(CPUFeatures, ' ');
       break;
     }

llvm/unittests/Support/ProgramTest.cpp

@@ -130,7 +130,7 @@ TEST_F(ProgramEnvTest, CreateProcessLongPath) {
   // prefix.
   sys::path::native(MyAbsExe, sys::path::Style::windows_backslash);
   std::string MyExe;
-  if (!StringRef(MyAbsExe).startswith("\\\\?\\"))
+  if (!StringRef(MyAbsExe).starts_with("\\\\?\\"))
     MyExe.append("\\\\?\\");
   MyExe.append(std::string(MyAbsExe.begin(), MyAbsExe.end()));
 

llvm/unittests/Support/TypeNameTest.cpp

@@ -35,7 +35,7 @@ TEST(TypeNameTest, Names) {
 #ifdef __clang__
   EXPECT_TRUE(S2Name.ends_with("S2")) << S2Name.str();
 #else
-  EXPECT_TRUE(S2Name.endswith("::S2")) << S2Name.str();
+  EXPECT_TRUE(S2Name.ends_with("::S2")) << S2Name.str();
 #endif
 #else
   EXPECT_EQ("UNKNOWN_TYPE", S1Name);