Add util function to remove trailing '\r'

Depending on the platform and adb versions, the lines output by adb
could end with "\r\r\n". This util function helps to remove all trailing
'\r'.

PR #2827 <https://github.com/Genymobile/scrcpy/pull/2827>

app/src/util/str.c

@@ -330,3 +330,14 @@ sc_str_index_of_column(const char *s, unsigned col, const char *seps) {
 
     return col == colidx ? (ssize_t) idx : -1;
 }
+
+size_t
+sc_str_remove_trailing_cr(char *s, size_t len) {
+    while (len) {
+        if (s[len - 1] != '\r') {
+            break;
+        }
+        s[--len] = '\0';
+    }
+    return len;
+}