Fix deadlocks during initialization (#167)

- More to come in later commit, below is just tidying some stuff up
  - clang-tidy
  - mpi_gotcha quiet about not finding funcs
  - update to new papi config
  - sampling block_samples / unblock_samples
    - disable calling component's sample functions within sampler
  - release doesn't strip library
  - remove HSA and ROCP env variables from modulefile / setup-env
- preliminary support for LD_PRELOAD usage
- default sampling rate is 300 interrupts / second
- fixes various deadlock issues at startup

source/lib/omnitrace/library/sampling.cpp

@@ -136,7 +136,8 @@ get_signal_names(Tp&& _v)
         _sig_names += std::get<0>(tim::signal_settings::get_info(
                           static_cast<tim::sys_signal>(itr))) +
                       " ";
-    return _sig_names.substr(0, _sig_names.length() - 1);
+    return (_sig_names.empty()) ? _sig_names
+                                : _sig_names.substr(0, _sig_names.length() - 1);
 }
 
 unique_ptr_t<sampler_t>&
@@ -418,6 +419,18 @@ shutdown()
     return configure(false);
 }
 
+void
+block_samples()
+{
+    trait::runtime_enabled<sampler_t>::set(false);
+}
+
+void
+unblock_samples()
+{
+    trait::runtime_enabled<sampler_t>::set(true);
+}
+
 void
 block_signals(std::set<int> _signals)
 {