Comment 5 for bug 1697528

SBCL 1.3.18 changelog contains :
"minor incompatible change: existing values of CFLAGS, ASFLAGS, CPPFLAGS, and LINKFLAGS will be incorporated into C compiler invocations when building from source. "

And the script used to build SBCL on Archlinux contains :
"
  export CFLAGS+=" -D_GNU_SOURCE -fno-omit-frame-pointer -DSBCL_HOME=/usr/lib/sbcl"
  export GNUMAKE="make"

  # build system uses LINKFLAGS and OS_LIBS to build LDFLAGS
  export LINKFLAGS="$LDFLAGS"
  unset LDFLAGS
  unset MAKEFLAGS
"

I don't know if it is important for the detection of the error by SBCL.