Set -Wno-vla.

Would have avoided 6e7255c17e1.

Change-Id: I94eeea70f6ee0b48c1a15b512d652579d65d0edf
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/37924
Commit-Queue: Adam Langley <alangley@gmail.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3fe86bf..15d1df2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -117,7 +117,7 @@
 if(CMAKE_COMPILER_IS_GNUCXX OR CLANG)
   # Note clang-cl is odd and sets both CLANG and MSVC. We base our configuration
   # primarily on our normal Clang one.
-  set(C_CXX_FLAGS "-Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings")
+  set(C_CXX_FLAGS "-Werror -Wformat=2 -Wsign-compare -Wmissing-field-initializers -Wwrite-strings -Wno-vla")
   if(MSVC)
     # clang-cl sets different default warnings than clang. It also treats -Wall
     # as -Weverything, to match MSVC. Instead -W3 is the alias for -Wall.