entry_name_utils-inl.h: clear top bit before shifting

Attempting to shift a uint8_t which has the top bit set results in a
value outside of the range allowable for a uint8_t. The process of
converting this value back to a uint8_t triggers ubsan's
implicit-conversion sanitizer.

Ensure the high order bit is stripped before shifting, so that the
shifted value fits into the allowable uint8_t range.

This change is necessary to enable integer sanitization on this code.

Somewhat related to Bug: 122975762
Test: atest ziparchive-tests

Change-Id: I940c8b2828ac88348d80f731274b990e35de6631

libziparchive/entry_name_utils-inl.h

@@ -35,7 +35,7 @@ inline bool IsValidEntryName(const uint8_t* entry_name, const size_t length) {
       return false;
     } else {
       // 2-5 byte sequences.
-      for (uint8_t first = byte << 1; first & 0x80; first <<= 1) {
+      for (uint8_t first = (byte & 0x7f) << 1; first & 0x80; first = (first & 0x7f) << 1) {
         ++i;
 
         // Missing continuation byte..