Added autoconf macro to check if soft and hard links really work, or are

just faked.

svn path=/trunk/boinc/; revision=6976

m4/sah_links.m4

@@ -0,0 +1,36 @@
+AC_DEFUN([SAH_LINKS],[
+  AC_PATH_PROGS(LN,[ln cp copy])
+  if test -n "$LN" ; then
+    AC_MSG_CHECKING(whether '$LN' works)
+    if $LN config.sub erase.me$$ && \
+       test -e erase.me$$ && \
+       diff config.sub erase.me$$ >/dev/null 2>&5 
+    then
+      AC_MSG_RESULT(yes)
+    else
+      AC_MSG_RESULT(no)
+      LN=cp
+    fi
+    /bin/rm erase.me$$
+  else
+    LN=cp
+  fi
+  AC_PROG_LN_S
+  if test -n "$LN_S" ; then
+    AC_MSG_CHECKING(whether '$LN_S' really works or whether I'm deluding myself)
+    if $LN_S config.sub erase.me$$ && \
+       test -e erase.me$$ && \
+       diff config.sub erase.me$$ >/dev/null 2>&5 
+    then
+      AC_MSG_RESULT(it works)
+    else
+      AC_MSG_RESULT(I'm deluding myself)
+      LN_S=cp
+    fi
+    /bin/rm erase.me$$
+  else
+    LN_S=cp
+  fi
+])  
+  
+