build: add gdb and valgrind support to the run-dtrace wrapper

Now, rather than having to mess around setting SYSLIBDIR and
LD_LIBRARY_PATH yourself to debug a just-built dtrace, you can
just run DTRACE_GDB=t build/run-dtrace or
DTRACE_VALGRIND=t build/run-dtrace

GDB is run with --args. Valgrind is run with no args other that the
just-built dtrace's for now.

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

cmd/Build

@@ -1,5 +1,5 @@
 # Oracle Linux DTrace.
-# Copyright (c) 2011, 2022, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2023, Oracle and/or its affiliates. All rights reserved.
 # Licensed under the Universal Permissive License v 1.0 as shown at
 # http://oss.oracle.com/licenses/upl.
 
@@ -27,16 +27,24 @@ bpf_dump_LIBS = -lelf
 
 $(objdir)/run-dtrace: $(DTRACE)
 	printf > $@ "\
-#!/bin/sh\n\
+#!/bin/bash\n\
 # run-dtrace -- A wrapper to run DTrace out of the build tree, or from /usr/sbin\n\
 #               if this is a check-installed run\n\
 \n\
-if [ -z \$$_DTRACE_CHECK_INSTALLED ]; then\n\
+if [[ -z \$$_DTRACE_CHECK_INSTALLED ]]; then\n\
     export DTRACE_OPT_SYSLIBDIR=$(objdir)/dlibs\n\
     export LD_LIBRARY_PATH=$(objdir)\n\
-    exec $(objdir)/dtrace \"\$$@\"\n\
+    dtrace_cmd=$(objdir)/dtrace\n\
 else\n\
-    exec /usr/sbin/dtrace \"\$$@\"\n\
+    dtrace_cmd=/usr/sbin/dtrace\n\
+fi\n\
+\n\
+if [[ -n \$$DTRACE_GDB ]]; then\n\
+    exec gdb --args \$$dtrace_cmd \"\$$@\"\n\
+elif [[ -n \$$DTRACE_VALGRIND ]]; then\n\
+    exec valgrind \$$dtrace_cmd \"\$$@\"\n\
+else\n\
+    exec \$$dtrace_cmd \"\$$@\"\n\
 fi\n"
 	chmod a+x $(objdir)/run-dtrace