Do not require owning strings for startsWith.

By passing in a `const std::string&` we would have incurred construction
costs of an owning string when all we needed was a non-owning view.

We also clean up the implementation of `startsWith` to use standard
library functionality.

hilti/runtime/include/util.h

@@ -240,7 +240,7 @@ std::string replace(std::string s, std::string_view o, std::string_view n);
  *
  * \note This function is not UTF8-aware.
  */
-bool startsWith(const std::string& s, const std::string& prefix);
+bool startsWith(std::string_view s, std::string_view prefix);
 
 /**
  * Python-style enumerate() that returns an iterable yielding pairs `(index,

hilti/runtime/src/tests/util.cc

@@ -148,7 +148,7 @@ TEST_CASE("createTemporaryFile") {
         SUBCASE("custom prefix") {
             auto prefix = "1234567890";
             tmp = createTemporaryFile(prefix).valueOrThrow();
-            CHECK(startsWith(tmp.filename(), prefix));
+            CHECK(startsWith(tmp.filename().string(), prefix));
         }
 
         CAPTURE(tmp);

hilti/runtime/src/util.cc

@@ -381,17 +381,7 @@ std::string hilti::rt::replace(std::string s, std::string_view o, std::string_vi
     return s;
 }
 
-bool hilti::rt::startsWith(const std::string& s, const std::string& prefix) {
-    if ( s.size() < prefix.size() )
-        return false;
-
-    for ( size_t i = 0; i < prefix.size(); ++i ) {
-        if ( s[i] != prefix[i] )
-            return false;
-    }
-
-    return true;
-}
+bool hilti::rt::startsWith(std::string_view s, std::string_view prefix) { return s.substr(0, prefix.size()) == prefix; }
 
 hilti::rt::ByteOrder hilti::rt::systemByteOrder() {
 #ifdef LITTLE_ENDIAN