nicer scons output (#37455)

SConstruct

@@ -18,6 +18,7 @@ AddOption('--asan', action='store_true', help='turn on ASAN')
 AddOption('--ubsan', action='store_true', help='turn on UBSan')
 AddOption('--mutation', action='store_true', help='generate mutation-ready code')
 AddOption('--ccflags', action='store', type='string', default='', help='pass arbitrary flags over the command line')
+AddOption('--verbose', action='store_true', default=False, help='show full build commands')
 AddOption('--minimal',
           action='store_false',
           dest='extras',
@@ -148,6 +149,22 @@ if _extra_cc:
 if arch != "Darwin":
   env.Append(LINKFLAGS=["-Wl,--as-needed", "-Wl,--no-undefined"])
 
+# Shorter build output: show brief descriptions instead of full commands.
+# Full command lines are still printed on failure by scons.
+if not GetOption('verbose'):
+  for action, short in (
+    ("CC",     "CC"),
+    ("CXX",    "CXX"),
+    ("LINK",   "LINK"),
+    ("SHCC",   "CC"),
+    ("SHCXX",  "CXX"),
+    ("SHLINK", "LINK"),
+    ("AR",     "AR"),
+    ("RANLIB", "RANLIB"),
+    ("AS",     "AS"),
+  ):
+    env[f"{action}COMSTR"] = f"  [{short}] $TARGET"
+
 # progress output
 node_interval = 5
 node_count = 0