Reland "Add format-specifier warnings to SkDebugf."

This is a reland of e58831cd9578805634b986b434a20757277b3a36

Original change's description:
> Add format-specifier warnings to SkDebugf.
>
> This CL fixes up many existing format-specifier violations in Skia.
> Note that GCC has a warning for formatting nothing, so existing calls to
> `SkDebugf("")` have been removed, or replaced with `SkDebugf("%s", "")`.
> These were apparently meant to be used as a place to set a breakpoint.
>
> Some of our clients also use SkDebug with bad format specifiers, so this
> check is currently only enabled when SKIA_IMPLEMENTATION is true.
>
> Change-Id: I8177a1298a624c6936adc24e0d8f481362a356d0
> Bug: skia:12143
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/420902
> Auto-Submit: John Stiles <johnstiles@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:12143
Change-Id: Id3c0c21436ebd13899908d5ed5d44c42a0e23921
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/421918
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/sksl/SkSLOperators.h b/src/sksl/SkSLOperators.h
index a51985f..4a936b0 100644
--- a/src/sksl/SkSLOperators.h
+++ b/src/sksl/SkSLOperators.h
@@ -22,7 +22,7 @@
 
     // Allow implicit conversion from Token::Kind, since this is just a utility wrapper on top.
     Operator(Token::Kind t) : fKind(t) {
-        SkASSERTF(this->isOperator(), "token-kind %d is not an operator", fKind);
+        SkASSERTF(this->isOperator(), "token-kind %d is not an operator", (int)fKind);
     }
 
     enum class Precedence {