bricks: add missing override

* bricks/brick-assert.h, bricks/brick-hashset.h,
bricks/brick-shmem.h: here.

bricks/brick-assert.h

@@ -132,7 +132,7 @@ struct AssertFailed : std::exception {
         (*this) << ": assertion `" << l.stmt << "' failed;";
     }
 
-    const char *what() const noexcept { return str.c_str(); }
+    const char *what() const noexcept override { return str.c_str(); }
 };
 
 template< typename Location, typename X >

bricks/brick-hashset.h

@@ -995,7 +995,7 @@ struct Parallel
         int from, to;
         bool overlap;
 
-        void main() {
+        void main() override {
             auto set = _set->withTD( td );
             for ( int i = from; i < to; ++i ) {
                 set.insert( i );

bricks/brick-shmem.h

@@ -551,7 +551,7 @@ struct FifoTest {
         int terminate;
         int n;
 
-        void main()
+        void main() override
         {
             std::vector< int > x;
             x.resize( n );
@@ -603,7 +603,7 @@ struct Utils {
             rep( repeat )
         {}
 
-        void main() {
+        void main() override {
             for ( int i = 0; i < rep; ++i )
                 detector.waitForAll( peers );
         }
@@ -648,7 +648,7 @@ struct Utils {
             consume( 0 )
         {}
 
-        void main() {
+        void main() override {
             detector.waitForAll( peers );
 
             while ( produce-- )