Add a kernel option for amd64 to compile with the frame on the stack

so that the DTrace Function Bounadry Trace (fbt) provider can get
coverage of most functions in the kernel.

sys/conf/Makefile.amd64

@@ -32,8 +32,9 @@ S=	../../..
 .include "$S/conf/kern.pre.mk"
 
 DDB_ENABLED!=	grep DDB opt_ddb.h || true
+DTR_ENABLED!=	grep KDTRACE_FRAME opt_kdtrace.h || true
 HWPMC_ENABLED!=	grep HWPMC opt_hwpmc_hooks.h || true
-.if !empty(DDB_ENABLED) || !empty(HWPMC_ENABLED)
+.if !empty(DDB_ENABLED) || !empty(DTR_ENABLED) || !empty(HWPMC_ENABLED)
 CFLAGS+=	-fno-omit-frame-pointer
 .endif
 

sys/conf/options.amd64

@@ -63,6 +63,7 @@ DEV_ATPIC		opt_atpic.h
 
 # Debugging
 STOP_NMI		opt_cpu.h
+KDTRACE_FRAME		opt_kdtrace.h
 
 # BPF just-in-time compiler
 BPF_JITTER		opt_bpf.h