[OpenMP] libomp: Fix handling of barrier pattern environment variables

[t-msn]

Summary

It is better to set all barrier patterns to use "dist" when at least
one environment variable specifies "dist". Otherwise if only one
environment is set to "dist" and others left blank inadvertently,
it would result in mixing dist barrier with default hyper barrier
pattern.

[t-msn]

Hello, this is the first time I submitted a patch and please let me know if I misunderstood something.

[tlwilmar]

LGTM

[t-msn]

As I don't have access right, would you mind committing this instead of me?

openmp/runtime/src/kmp_settings.cpp

if ((strcmp(var, name) == 0) && (value != 0)) {
                     KMP_MSG(BarrReleaseValueInvalid, name, comma + 1),
                     __kmp_msg_null);
           KMP_INFORM(Using_str_Value, name,
                      __kmp_barrier_pattern_name[bp_linear_bar]);
         }
       }
     }
   }
-  if ((dist_req == 0) && (non_dist_req != 0)) {
-    // Something was set to a barrier other than dist; set all others to hyper
-    for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
-      if (__kmp_barrier_release_pattern[i] == bp_dist_bar)
-        __kmp_barrier_release_pattern[i] = bp_hyper_bar;
-      if (__kmp_barrier_gather_pattern[i] == bp_dist_bar)
-        __kmp_barrier_gather_pattern[i] = bp_hyper_bar;
-    }
-  } else if (non_dist_req != 0) {
-    // some requests for dist, plus requests for others; set all to dist
-    if (non_dist_req > 0 && dist_req > 0 && warn) {
+  if (dist_req != 0) {
+    // set all barriers to dist
+    if ((non_dist_req != 0) && warn) {
       KMP_INFORM(BarrierPatternOverride, name,
                  __kmp_barrier_pattern_name[bp_dist_bar]);
       warn = 0;
     }
     for (int i = bs_plain_barrier; i < bs_last_barrier; i++) {
       if (__kmp_barrier_release_pattern[i] != bp_dist_bar)
         __kmp_barrier_release_pattern[i] = bp_dist_bar;
       if (__kmp_barrier_gather_pattern[i] != bp_dist_bar)