pre/CMakeLists.txt defines CMAKE_DEBUG_POSTFIX which causes a different
library name on Windows debug build (pcred.lib rather than pre.lib)
However MERGE_LIBRARIES macro that is used to create static embedded
library (out of other static libraries), can not handle per-configuration
library names. Thus the build fails with "pre.lib not found"
Fix is to remove unnecessary CMAKE_DEBUG_POSTFIX
PCRE unit tests failed on Ubuntu Precise, because "source"
is not a known command in "dash" (the default shell in Precise).
Changing "source" to ".", which should be understood in all shells.
libmysqld.a(pcre_exec.c.o): relocation R_X86_64_32S against
`_pcre_ucd_stage1' can not be used when making a shared object;
make[2]: Leaving directory `/mnt/buildbot/build/mariadb-10.0.3'
recompile with -fPIC
Changing ADD_LIBRARY(pcre) to ADD_CONVENIENCE_LIBRARY(pcre)
