clang 7.0.1 build fails with `error: argument unused during compilation: '-Qn'`

[Paul Menzel]

Dear GRUB folks,


Building GRUB from the master branch fails with clang 7.0.1 fails
with the error below. The error is not shown with clang 6.0.1.

```
$ ./autogen.sh
$ ./configure CC=clang
$ make -j`nproc`
[…]
clang -DHAVE_CONFIG_H -I. -I..  -Wall -W  -DGRUB_MACHINE_PCBIOS=1 
-DGRUB_MACHINE=I386_PC -m32 -msoft-float -Xclang -msoft-float -Xclang 
-no-implicit-float -nostdinc -isystem /usr/lib/clang/7.0.1/include -I../include 
-I../include -DGRUB_FILE=\"bus/cs5536.c\" -I. -I. -I.. -I.. -I../include 
-I../include -I../grub-core/lib/libgcrypt-grub/src/    -D_FILE_OFFSET_BITS=64 
-Os -Wall -W -Wshadow -Wpointer-arith -Wundef -Wchar-subscripts -Wcomment 
-Wdeprecated-declarations -Wdisabled-optimization -Wdiv-by-zero -Wfloat-equal 
-Wformat-extra-args -Wformat-security -Wformat-y2k -Wimplicit 
-Wimplicit-function-declaration -Wimplicit-int -Wmain -Wmissing-braces 
-Wmissing-format-attribute -Wmultichar -Wparentheses -Wreturn-type 
-Wsequence-point -Wshadow -Wsign-compare -Wswitch -Wtrigraphs -Wunknown-pragmas 
-Wunused -Wunused-function -Wunused-label -Wunused-parameter -Wunused-value  
-Wunused-variable -Wwrite-strings -Wnested-externs -Wstrict-prototypes -g 
-Wredundant-decls -Wmissing-prototypes -Wmissing-declarations  -Wextra 
-Wattributes -Wendif-labels -Winit-self -Wint-to-pointer-cast -Winvalid-pch 
-Wmissing-field-initializers -Wnonnull -Woverflow -Wvla -Wpointer-to-int-cast 
-Wstrict-aliasing -Wvariadic-macros -Wvolatile-register-var -Wpointer-sign 
-Wmissing-include-dirs -Wmissing-prototypes -Wmissing-declarations -Wformat=2 
-march=i386 -m32 -malign-jumps=1 -malign-loops=1 -malign-functions=1 
-freg-struct-return -mno-mmx -mno-sse -mno-sse2 -mno-sse3 -mno-3dnow 
-fno-dwarf2-cfi-asm -mno-stack-arg-probe -fno-asynchronous-unwind-tables 
-fno-unwind-tables -Qn -fno-stack-protector -Werror   -ffreestanding   -MT 
bus/cs5536_module-cs5536.o -MD -MP -MF bus/.deps-core/cs5536_module-cs5536.Tpo 
-c -o bus/cs5536_module-cs5536.o `test -f 'bus/cs5536.c' || echo 
'./'`bus/cs5536.c
clang-7grep 'MARKER' gcry_twofish.marker.new > gcry_twofish.marker; rm -f 
gcry_twofish.marker.new
: error: argument unused during compilation: '-Qn' 
[-Werror,-Wunused-command-line-argument]
make[3]: *** [Makefile:28232: trig.module] Error 1
```


Kind regards,

Paul

smime.p7s
Description: S/MIME Cryptographic Signature