Meta: Switch to the Lagom directory before building fuzzers

This confused quite a number of people in the past, and it is still
slightly annoying to always switch the directory when testing both the
OS and the fuzzer build. Instead, let's just switch to the correct
directory automatically.

Meta/Lagom/BuildFuzzers.sh

@@ -2,6 +2,9 @@
 
 set -e
 
+SCRIPT_PATH="$(dirname "${0}")"
+cd "${SCRIPT_PATH}"
+
 BEST_CLANG_CANDIDATE=""
 
 die() {