Some compilers don't have -Wvla.

Index: lib/libzstd.mk
--- lib/libzstd.mk.orig
+++ lib/libzstd.mk
@@ -92,7 +92,7 @@ endif
 DEBUGFLAGS= -Wall -Wextra -Wcast-qual -Wcast-align -Wshadow \
             -Wstrict-aliasing=1 -Wswitch-enum -Wdeclaration-after-statement \
             -Wstrict-prototypes -Wundef -Wpointer-arith \
-            -Wvla -Wformat=2 -Winit-self -Wfloat-equal -Wwrite-strings \
+            -Wformat=2 -Winit-self -Wfloat-equal -Wwrite-strings \
             -Wredundant-decls -Wmissing-prototypes -Wc++-compat
 CFLAGS   += $(DEBUGFLAGS) $(MOREFLAGS)
 ASFLAGS  += $(DEBUGFLAGS) $(MOREFLAGS) $(CFLAGS)
