Patch borrowed from
http://code.google.com/p/minimyth/source/browse/trunk/gar-minimyth/script/db/mysql/files/mysql-5.1.47-ac_cache_check.patch?r=6493.

It allows to override through ac_cv_* variables various checks that
cannot be performed when cross-compiling.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

diff -Naur mysql-5.1.47-old/storage/innodb_plugin/plug.in mysql-5.1.47-new/storage/innodb_plugin/plug.in
--- mysql-5.1.47-old/storage/innodb_plugin/plug.in	2010-05-20 09:55:10.000000000 -0700
+++ mysql-5.1.47-new/storage/innodb_plugin/plug.in	2010-05-20 09:56:12.000000000 -0700
@@ -53,9 +53,10 @@
   esac
   AC_SUBST(INNODB_DYNAMIC_CFLAGS)
 
-  AC_MSG_CHECKING(whether GCC atomic builtins are available)
+  AC_CACHE_CHECK([whether GCC atomic builtins are available],
+                 [ac_cv_have_decl_HAVE_IB_GCC_ATOMIC_BUILTINS],
   # either define HAVE_IB_GCC_ATOMIC_BUILTINS or not
-  AC_TRY_RUN(
+  [AC_TRY_RUN(
     [
       int main()
       {
@@ -95,18 +96,23 @@
       }
     ],
     [
-      AC_DEFINE([HAVE_IB_GCC_ATOMIC_BUILTINS], [1],
-                [GCC atomic builtins are available])
       AC_MSG_RESULT(yes)
+      ac_cv_have_decl_HAVE_IB_GCC_ATOMIC_BUILTINS=yes
     ],
     [
       AC_MSG_RESULT(no)
+      ac_cv_have_decl_HAVE_IB_GCC_ATOMIC_BUILTINS=no
     ]
-  )
+  )])
+  if test "x$ac_cv_have_decl_HAVE_IB_GCC_ATOMIC_BUILTINS"= "xyes" ; then
+    AC_DEFINE([HAVE_IB_GCC_ATOMIC_BUILTINS], [1],
+              [GCC atomic builtins are available])
+  fi
 
-  AC_MSG_CHECKING(whether pthread_t can be used by GCC atomic builtins)
+  AC_CACHE_CHECK([whether pthread_t can be used by GCC atomic builtins],
+                 [ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_GCC],
   # either define HAVE_IB_ATOMIC_PTHREAD_T_GCC or not
-  AC_TRY_RUN(
+  [AC_TRY_RUN(
     [
       #include <pthread.h>
       #include <string.h>
@@ -126,14 +132,18 @@
       }
     ],
     [
-      AC_DEFINE([HAVE_IB_ATOMIC_PTHREAD_T_GCC], [1],
-                [pthread_t can be used by GCC atomic builtins])
       AC_MSG_RESULT(yes)
+      ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_GCC=yes
     ],
     [
       AC_MSG_RESULT(no)
+      ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_GCC=no
     ]
-  )
+  )])
+  if test "x$ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_GCC"= "xyes" ; then
+    AC_DEFINE([HAVE_IB_ATOMIC_PTHREAD_T_GCC], [1],
+              [pthread_t can be used by GCC atomic builtins])
+  fi
 
   AC_MSG_CHECKING(whether Solaris libc atomic functions are available)
   # either define HAVE_IB_SOLARIS_ATOMICS or not
@@ -147,9 +157,10 @@
 			    are available])
   )
 
-  AC_MSG_CHECKING(whether pthread_t can be used by Solaris libc atomic functions)
+  AC_CACHE_CHECK([whether pthread_t can be used by Solaris libc atomic functions],
+                 [ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS],
   # either define HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS or not
-  AC_TRY_RUN(
+  [AC_TRY_RUN(
     [
       #include <pthread.h>
       #include <string.h>
@@ -180,28 +191,33 @@
       }
     ],
     [
-      AC_DEFINE([HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS], [1],
-                [pthread_t can be used by solaris atomics])
       AC_MSG_RESULT(yes)
+      ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS=yes
     ],
     [
       AC_MSG_RESULT(no)
+      ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS=no
     ]
-  )
+  )])
+  if test "x$ac_cv_have_decl_HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS"= "xyes" ; then
+    AC_DEFINE([HAVE_IB_ATOMIC_PTHREAD_T_SOLARIS], [1],
+              [pthread_t can be used by solaris atomics])
+  fi
 
   # this is needed to know which one of atomic_cas_32() or atomic_cas_64()
   # to use in the source
   AC_CHECK_SIZEOF([pthread_t], [], [#include <pthread.h>])
 
   # Check for x86 PAUSE instruction
-  AC_MSG_CHECKING(for x86 PAUSE instruction)
+  AC_CACHE_CHECK([for x86 PAUSE instruction],
+                 [ac_cv_have_decl_HAVE_IB_PAUSE_INSTRUCTION],
   # We have to actually try running the test program, because of a bug
   # in Solaris on x86_64, where it wrongly reports that PAUSE is not
   # supported when trying to run an application. See
   # http://bugs.opensolaris.org/bugdatabase/printableBug.do?bug_id=6478684
   # We use ib_ prefix to avoid collisoins if this code is added to
   # mysql's configure.in.
-  AC_TRY_RUN(
+  [AC_TRY_RUN(
     [
       int main() {
         __asm__ __volatile__ ("pause");
@@ -209,16 +225,21 @@
       }
     ],
     [
-      AC_DEFINE([HAVE_IB_PAUSE_INSTRUCTION], [1], [Does x86 PAUSE instruction exist])
       AC_MSG_RESULT(yes)
+      ac_cv_have_decl_HAVE_IB_PAUSE_INSTRUCTION=yes
     ],
     [
       AC_MSG_RESULT(no)
+      ac_cv_have_decl_HAVE_IB_PAUSE_INSTRUCTION=no
     ],
     [
       AC_MSG_RESULT(no)
+      ac_cv_have_decl_HAVE_IB_PAUSE_INSTRUCTION=no
     ]
-  )
+  )])
+  if test "x$ac_cv_have_decl_HAVE_IB_PAUSE_INSTRUCTION"= "xyes" ; then
+    AC_DEFINE([HAVE_IB_PAUSE_INSTRUCTION], [1], [Does x86 PAUSE instruction exist])
+  fi
   ])
 
 # vim: set ft=config: