configure: Fix creation of symbolic links for MinGW toolchain

The MinGW toolchain on w32/w64 hosts does not create symbolic links,
but implements 'ln -s' similar to 'cp -r'.

In incremental out of tree builds, this resulted in files which
were not updated when their counterparts in the QEMU source tree
changed. Especially for Makefile* this happened very often.

With this patch, the 'symlinked' files are now always updated for
out of tree builds. Similar code was already used for the symbolic
link of libcacard/Makefile.

The symlink macro always removes the target before it is created
again, therefore the rm command for libcacard/Makefile was redundant
and is removed now.

Macro symlink is also used with directories. To remove them on w32
hosts, a recursive rm is needed.

v2:
Quote arguments in shell function symlink, and also quote any argument
which is passed to symlink and which contains macros. This should reduce
the chance of accidents caused by rm -rf.

Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

configure

@@ -41,8 +41,8 @@ compile_prog() {
 
 # symbolically link $1 to $2.  Portable version of "ln -sf".
 symlink() {
-  rm -f $2
-  ln -s $1 $2
+  rm -rf "$2"
+  ln -s "$1" "$2"
 }
 
 # check whether a command is available to this shell (may be either an
@@ -3435,7 +3435,7 @@ fi
 
 for d in libdis libdis-user; do
     mkdir -p $d
-    symlink $source_path/Makefile.dis $d/Makefile
+    symlink "$source_path/Makefile.dis" "$d/Makefile"
     echo > $d/config.mak
 done
 
@@ -3444,13 +3444,13 @@ if test "$linux" = "yes" ; then
   mkdir -p linux-headers
   case "$cpu" in
   i386|x86_64)
-    symlink $source_path/linux-headers/asm-x86 linux-headers/asm
+    symlink "$source_path/linux-headers/asm-x86" linux-headers/asm
     ;;
   ppcemb|ppc|ppc64)
-    symlink $source_path/linux-headers/asm-powerpc linux-headers/asm
+    symlink "$source_path/linux-headers/asm-powerpc" linux-headers/asm
     ;;
   s390x)
-    symlink $source_path/linux-headers/asm-s390 linux-headers/asm
+    symlink "$source_path/linux-headers/asm-s390" linux-headers/asm
     ;;
   esac
 fi
@@ -3515,7 +3515,7 @@ mkdir -p $target_dir/kvm
 if test "$target" = "arm-linux-user" -o "$target" = "armeb-linux-user" -o "$target" = "arm-bsd-user" -o "$target" = "armeb-bsd-user" ; then
   mkdir -p $target_dir/nwfpe
 fi
-symlink $source_path/Makefile.target $target_dir/Makefile
+symlink "$source_path/Makefile.target" "$target_dir/Makefile"
 
 
 echo "# Automatically generated by configure - do not modify" > $config_target_mak
@@ -3958,7 +3958,7 @@ do
 done
 mkdir -p $DIRS
 for f in $FILES ; do
-    if [ -e "$source_path/$f" ] && ! [ -e "$f" ]; then
+    if [ -e "$source_path/$f" ] && [ "$source_path" != `pwd` ]; then
         symlink "$source_path/$f" "$f"
     fi
 done
@@ -3981,7 +3981,7 @@ for hwlib in 32 64; do
   mkdir -p $d
   mkdir -p $d/ide
   mkdir -p $d/usb
-  symlink $source_path/Makefile.hw $d/Makefile
+  symlink "$source_path/Makefile.hw" "$d/Makefile"
   mkdir -p $d/9pfs
   echo "QEMU_CFLAGS+=-DTARGET_PHYS_ADDR_BITS=$hwlib" > $d/config.mak
 done
@@ -3989,7 +3989,6 @@ done
 if [ "$source_path" != `pwd` ]; then
     # out of tree build
     mkdir -p libcacard
-    rm -f libcacard/Makefile
     symlink "$source_path/libcacard/Makefile" libcacard/Makefile
 fi
 
@@ -3997,7 +3996,7 @@ d=libuser
 mkdir -p $d
 mkdir -p $d/trace
 mkdir -p $d/qom
-symlink $source_path/Makefile.user $d/Makefile
+symlink "$source_path/Makefile.user" "$d/Makefile"
 
 if test "$docs" = "yes" ; then
   mkdir -p QMP