configure: do not invoke as/ld directly for pc-bios/optionrom

Just use using the compiler binary, with -nostdlib in the case of the
linker; the compiler driver (whether i686-*-gcc, or x86_64-*-gcc with
the -m32 option) will then pick the right magic option to as and ld.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/configure b/configure
index cc4ecd6..894e373 100755
--- a/configure
+++ b/configure
@@ -2320,23 +2320,11 @@
 if test -n "$target_cc" &&
         test "$targetos" != "darwin" && test "$targetos" != "sunos" && \
         test "$targetos" != "haiku" && test "$softmmu" = yes ; then
-    # Different host OS linkers have different ideas about the name of the ELF
-    # emulation. Linux and OpenBSD/amd64 use 'elf_i386'; FreeBSD uses the _fbsd
-    # variant; OpenBSD/i386 uses the _obsd variant; and Windows uses i386pe.
-    for emu in elf_i386 elf_i386_fbsd elf_i386_obsd i386pe; do
-        if "$target_ld" -verbose 2>&1 | grep -q "^[[:space:]]*${emu}[[:space:]]*$"; then
-            ld_i386_emulation="$emu"
-            break
-        fi
-    done
-    if test -n "$ld_i386_emulation"; then
-        roms="pc-bios/optionrom"
-        config_mak=pc-bios/optionrom/config.mak
-        echo "# Automatically generated by configure - do not modify" > $config_mak
-        echo "TOPSRC_DIR=$source_path" >> $config_mak
-        echo "LD_I386_EMULATION=$ld_i386_emulation" >> $config_mak
-        write_target_makefile >> $config_mak
-    fi
+    roms="pc-bios/optionrom"
+    config_mak=pc-bios/optionrom/config.mak
+    echo "# Automatically generated by configure - do not modify" > $config_mak
+    echo "TOPSRC_DIR=$source_path" >> $config_mak
+    write_target_makefile >> $config_mak
 fi
 
 probe_target_compiler ppc-softmmu