cmd/compile: correct capitalization in recordFlags parameter

Tool refactoring smallStacks into smallFrames helpfully
"corrected" the capitalization in a string, this undoes
the help.

This is necessary to ensure correct (re)building when the
flag is used to research stack-marking GC latency bugs.

Updates #27732.

Change-Id: Ib7c8d4a36c9e4f9612559be68bd481f9d9cc69f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/180958
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/gc/main.go

@@ -272,7 +272,7 @@ func Main(archInit func(*Arch)) {
 	// Record flags that affect the build result. (And don't
 	// record flags that don't, since that would cause spurious
 	// changes in the binary.)
-	recordFlags("B", "N", "l", "msan", "race", "shared", "dynlink", "dwarflocationlists", "newescape", "dwarfbasentries", "smallFrames")
+	recordFlags("B", "N", "l", "msan", "race", "shared", "dynlink", "dwarflocationlists", "newescape", "dwarfbasentries", "smallframes")
 
 	if smallFrames {
 		maxStackVarSize = 128 * 1024