fix: Don't let fmtlib exceptions crash the app

When fmt arguments don't match the format string, fmt will throw an
exception, or terminate if we disable exceptions (which we do).  For
gcc11+, we tried intercepting these, but let's do it for all platform,
and let's not terminate ourselves, but insted print and log the error.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

src/include/OpenImageIO/detail/fmt.h

@@ -19,13 +19,13 @@
 #    define FMT_EXCEPTIONS 0
 #endif
 
-// Redefining FMT_THROW to something benign seems to avoid some UB or possibly
-// gcc 11+ compiler bug triggered by the definition of FMT_THROW in fmt 10.1+
-// when FMT_EXCEPTIONS=0, which results in mangling SIMD math. This nugget
-// below works around the problems for hard to understand reasons.
-#if !defined(FMT_THROW) && !FMT_EXCEPTIONS && OIIO_GNUC_VERSION >= 110000
+// Redefining FMT_THROW to print and log the error. This should only occur if
+// we've made a mistake and mismatched a format string and its arguments.
+// Hopefully this will help us track it down.
+#if !defined(FMT_THROW) && !FMT_EXCEPTIONS
 #    define FMT_THROW(x) \
-        OIIO_ASSERT_MSG(0, "fmt exception: %s", (x).what()), std::terminate()
+        OIIO::print("fmt exception: {}", (x).what()), \
+        OIIO::errorfmt("fmt exception: {}", (x).what())
 #endif
 
 // Use the grisu fast floating point formatting for old fmt versions