error while installing auto_explain contrib module

Hi,

I am trying to install auto_explain on PostgreSQL-9.3.11
OS X EI Capitan - 10.11

I am getting following error:

------
$ pwd
/Users/sachin/postgres_git/postgres/contrib/auto_explain

$ make
gcc -g -O0 -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute
-Wformat-security -fno-strict-aliasing -fwrapv
-Wno-unused-command-line-argument -g -pg -I. -I. -I../../src/include
-I/opt/local/include/libxml2 -c -o auto_explain.o auto_explain.c
gcc -g -O0 -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute
-Wformat-security -fno-strict-aliasing -fwrapv
-Wno-unused-command-line-argument -g -pg -bundle -multiply_defined
suppress -o auto_explain.so auto_explain.o -L../../src/port
-L../../src/common -L/opt/local/lib -Wl,-dead_strip_dylibs
-bundle_loader ../../src/backend/postgres
ld: warning: directory not found for option '-L/usr/local/lib'
Undefined symbols for architecture x86_64:
"_MemoryContextSwitchTo", referenced from:
_explain_ExecutorStart in auto_explain.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
make: *** [auto_explain.so] Error 1

--

Thanks and Regards,
Sachin Kotwal