mysql 5.5's new cmake-based build scripts forgot about defining
DEFAULT_HOME_ENV.  Upstream at http://bugs.mysql.com/bug.php?id=59280


diff -Naur mysql-5.5.8.orig/mysys/CMakeLists.txt mysql-5.5.8/mysys/CMakeLists.txt
--- mysql-5.5.8.orig/mysys/CMakeLists.txt	2010-12-03 12:58:26.000000000 -0500
+++ mysql-5.5.8/mysys/CMakeLists.txt	2011-01-13 11:58:42.583471734 -0500
@@ -69,6 +69,8 @@
  SET(MYSYS_SOURCES ${MYSYS_SOURCES} my_port.c)
 ENDIF()
 
+ADD_DEFINITIONS( -DDEFAULT_HOME_ENV=MYSQL_HOME)
+
 ADD_CONVENIENCE_LIBRARY(mysys ${MYSYS_SOURCES})
 TARGET_LINK_LIBRARIES(mysys dbug strings ${ZLIB_LIBRARY} 
  ${LIBNSL} ${LIBM} ${LIBRT})