tests/tcg: don't allow clang as a cross compiler

Currently there are two problems.

The first is clang generates a preamble (that is always executed) to
stack xmm registers. This causes a ILLOP on the x86_64 softmmu tests
as SSE isn't enabled.

The second is the inline assembler in test-i386.c breaks clangs
compiler and I don't know how to fix it. Even with Theodore's patch
series (D5741445-7EFD-4AF1-8DB2-E4AFA93CBB1A@icloud.com) I still get
compiler failures.

For now lets just skip clang and allow it to fall back to the
containers which we know have compilers which work.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210512102051.12134-31-alex.bennee@linaro.org>

tests/tcg/configure.sh

@@ -82,6 +82,9 @@ for target in $target_list; do
   container_cross_as=
   container_cross_ld=
 
+  # suppress clang
+  supress_clang=
+
   case $target in
     aarch64-*)
       # We don't have any bigendian build tools so we only use this for AArch64
@@ -119,6 +122,7 @@ for target in $target_list; do
       container_hosts=x86_64
       container_image=fedora-i386-cross
       container_cross_cc=gcc
+      supress_clang=yes
       ;;
     m68k-*)
       container_hosts=x86_64
@@ -186,6 +190,7 @@ for target in $target_list; do
       container_hosts="aarch64 ppc64el x86_64"
       container_image=debian-amd64-cross
       container_cross_cc=x86_64-linux-gnu-gcc
+      supress_clang=yes
       ;;
     xtensa*-softmmu)
       container_hosts=x86_64
@@ -200,6 +205,7 @@ for target in $target_list; do
 
   echo "# Automatically generated by configure - do not modify" > $config_target_mak
   echo "TARGET_NAME=$arch" >> $config_target_mak
+  echo "target=$target" >> $config_target_mak
   case $target in
     *-linux-user | *-bsd-user)
       echo "CONFIG_USER_ONLY=y" >> $config_target_mak
@@ -219,7 +225,11 @@ for target in $target_list; do
   if eval test "x\${cross_cc_$arch}" != xyes; then
       eval "target_compiler=\${cross_cc_$arch}"
 
-      if has $target_compiler; then
+      if has "$target_compiler"; then
+          if test "$supress_clang" = yes &&
+                  $target_compiler --version | grep -qi "clang"; then
+              got_cross_cc=no
+          else
               write_c_skeleton
               if ! do_compiler "$target_compiler" $target_compiler_cflags \
                    -o $TMPE $TMPC -static ; then
@@ -237,6 +247,7 @@ for target in $target_list; do
               fi
           fi
       fi
+  fi
 
   if test $got_cross_cc = yes; then
       # Test for compiler features for optional tests. We only do this