Update configure cache file example.

Author: jasone

INSTALL

@@ -328,19 +328,13 @@ PATH="?"
     'configure' uses this to find programs.
 
 In some cases it may be necessary to work around configuration results that do
-not match reality.  For example, OS X 10.12 in conjunction with XCode 8 adds
-the os_unfair_lock_*() API, but if XCode 8 is used to build jemalloc on older
-versions of OS X, the configure script will determine that os_unfair_lock_*()
-is compilable, yet run-time failures will result.  To work around this
-(ignoring that MACOSX_DEPLOYMENT_TARGET may be the correct fix), create a cache
-file (called e.g. darwin.cache) with the following contents to override the
-relevant configuration variable defined in configure.ac:
+not match reality.  For example, Linux 4.5 added support for the MADV_FREE flag
+to madvise(2), which can cause problems if building on a host with MADV_FREE
+support and deploying to a target without.  To work around this, use a cache
+file to override the relevant configuration variable defined in configure.ac,
+e.g.:
 
-    je_cv_os_unfair_lock=no
-
-Invoke configure as such:
-
-    ./configure --cache=darwin.cache
+    echo "je_cv_madv_free=no" > config.cache && ./configure -C
 
 === Advanced compilation =======================================================