[ELF] Respect --sysroot for INCLUDE

If an included script is under the sysroot directory, when it opens an
absolute path file (`INPUT` or `GROUP`), add sysroot before the absolute
path. When the included script ends, the `isUnderSysroot` state is
restored.

lld/ELF/ScriptParser.cpp

@@ -48,16 +48,6 @@ namespace {
 class ScriptParser final : ScriptLexer {
 public:
   ScriptParser(MemoryBufferRef mb) : ScriptLexer(mb) {
-    // Initialize IsUnderSysroot
-    if (config->sysroot == "")
-      return;
-    StringRef path = mb.getBufferIdentifier();
-    for (; !path.empty(); path = sys::path::parent_path(path)) {
-      if (!sys::fs::equivalent(config->sysroot, path))
-        continue;
-      isUnderSysroot = true;
-      return;
-    }
   }
 
   void readLinkerScript();
@@ -135,9 +125,6 @@ private:
   std::pair<SmallVector<SymbolVersion, 0>, SmallVector<SymbolVersion, 0>>
   readSymbols();
 
-  // True if a script being read is in the --sysroot directory.
-  bool isUnderSysroot = false;
-
   // If we are currently parsing a PROVIDE|PROVIDE_HIDDEN command,
   // then this member is set to the PROVIDE symbol name.
   std::optional<llvm::StringRef> activeProvideSym;
@@ -319,7 +306,7 @@ void ScriptParser::readNoCrossRefs(bool to) {
 }
 
 void ScriptParser::addFile(StringRef s) {
-  if (isUnderSysroot && s.starts_with("/")) {
+  if (curBuf.isUnderSysroot && s.starts_with("/")) {
     SmallString<128> pathData;
     StringRef path = (config->sysroot + s).toStringRef(pathData);
     if (sys::fs::exists(path))