[lsan][Fuchsia] Define EarlySanitizerInit for standalone lsan (#138946)

I forgot to add this definition in https://github.com/llvm/llvm-project/pull/131886.

compiler-rt/lib/lsan/lsan_fuchsia.cpp

@@ -21,6 +21,11 @@
 
 using namespace __lsan;
 
+namespace __sanitizer {
+// LSan doesn't need to do anything else special in the startup hook.
+void EarlySanitizerInit() {}
+}  // namespace __sanitizer
+
 namespace __lsan {
 
 void LsanOnDeadlySignal(int signo, void *siginfo, void *context) {}