example compile error

update to last commit, compile passed, but example still compile error.

$ go version
go version go1.2 darwin/amd64

 $ cd example/
 $ go build -x .
WORK=/var/folders/8g/k56fj_l17g32bg3fmjqqhgdr0000gp/T/go-build990910672
mkdir -p $WORK/github.com/mattn/go-mruby/_obj/
mkdir -p $WORK/github.com/mattn/
cd /opt/dev_study/study_go/src/github.com/mattn/go-mruby
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/cgo -objdir $WORK/github.com/mattn/go-mruby/_obj/ -- -I $WORK/github.com/mattn/go-mruby/_obj/ -Imruby/include mruby.go
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6c -F -V -w -I $WORK/github.com/mattn/go-mruby/_obj/ -I /usr/local/Cellar/go/1.2/libexec/pkg/darwin_amd64 -o $WORK/github.com/mattn/go-mruby/_obj/_cgo_defun.6 -D GOOS_darwin -D GOARCH_amd64 $WORK/github.com/mattn/go-mruby/_obj/_cgo_defun.c
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -print-libgcc-file-name
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -I $WORK/github.com/mattn/go-mruby/_obj/ -Imruby/include -o $WORK/github.com/mattn/go-mruby/_obj/_cgo_main.o -c $WORK/github.com/mattn/go-mruby/_obj/_cgo_main.c
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -I $WORK/github.com/mattn/go-mruby/_obj/ -Imruby/include -o $WORK/github.com/mattn/go-mruby/_obj/_cgo_export.o -c $WORK/github.com/mattn/go-mruby/_obj/_cgo_export.c
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -I $WORK/github.com/mattn/go-mruby/_obj/ -Imruby/include -o $WORK/github.com/mattn/go-mruby/_obj/mruby.cgo2.o -c $WORK/github.com/mattn/go-mruby/_obj/mruby.cgo2.c
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -o $WORK/github.com/mattn/go-mruby/_obj/_cgo_.o $WORK/github.com/mattn/go-mruby/_obj/_cgo_main.o $WORK/github.com/mattn/go-mruby/_obj/_cgo_export.o $WORK/github.com/mattn/go-mruby/_obj/mruby.cgo2.o -L mruby/build/host/lib -lmruby -lm
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/cgo -objdir $WORK/github.com/mattn/go-mruby/_obj/ -dynimport $WORK/github.com/mattn/go-mruby/_obj/_cgo_.o -dynout $WORK/github.com/mattn/go-mruby/_obj/_cgo_import.c
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6c -F -V -w -I $WORK/github.com/mattn/go-mruby/_obj/ -I /usr/local/Cellar/go/1.2/libexec/pkg/darwin_amd64 -o $WORK/github.com/mattn/go-mruby/_obj/_cgo_import.6 -D GOOS_darwin -D GOARCH_amd64 $WORK/github.com/mattn/go-mruby/_obj/_cgo_import.c
clang -I . -g -O2 -fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fno-common -o $WORK/github.com/mattn/go-mruby/_obj/_all.o $WORK/github.com/mattn/go-mruby/_obj/_cgo_export.o $WORK/github.com/mattn/go-mruby/_obj/mruby.cgo2.o -L mruby/build/host/lib -Wl,-r -nostdlib
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6g -o $WORK/github.com/mattn/go-mruby/_obj/_go_.6 -p github.com/mattn/go-mruby -D _/opt/dev_study/study_go/src/github.com/mattn/go-mruby -I $WORK $WORK/github.com/mattn/go-mruby/_obj/_cgo_gotypes.go $WORK/github.com/mattn/go-mruby/_obj/mruby.cgo1.go
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/pack grcP $WORK $WORK/github.com/mattn/go-mruby.a $WORK/github.com/mattn/go-mruby/_obj/_go_.6 $WORK/github.com/mattn/go-mruby/_obj/_cgo_import.6 $WORK/github.com/mattn/go-mruby/_obj/_cgo_defun.6 $WORK/github.com/mattn/go-mruby/_obj/_all.o
mkdir -p $WORK/github.com/mattn/go-mruby/example/_obj/
mkdir -p $WORK/github.com/mattn/go-mruby/example/_obj/exe/
cd /opt/dev_study/study_go/src/github.com/mattn/go-mruby/example
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6g -o $WORK/github.com/mattn/go-mruby/example/_obj/_go_.6 -p github.com/mattn/go-mruby/example -complete -D _/opt/dev_study/study_go/src/github.com/mattn/go-mruby/example -I $WORK -I /opt/dev_study/study_go/pkg/darwin_amd64 ./example.go
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/pack grcP $WORK $WORK/github.com/mattn/go-mruby/example.a $WORK/github.com/mattn/go-mruby/example/_obj/_go_.6
cd .
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6l -o $WORK/github.com/mattn/go-mruby/example/_obj/exe/a.out -L $WORK -L /opt/dev_study/study_go/pkg/darwin_amd64 $WORK/github.com/mattn/go-mruby/example.a
# github.com/mattn/go-mruby/example
ld: warning: directory not found for option '-Lmruby/build/host/lib'
ld: library not found for -lmruby
clang: error: linker command failed with exit code 1 (use -v to see invocation)
/usr/local/Cellar/go/1.2/libexec/pkg/tool/darwin_amd64/6l: running gcc failed: unsuccessful exit status 0x100

$ pwd
/opt/dev_study/study_go/src/github.com/mattn/go-mruby/example
$ ll ../mruby/build/host/lib/
total 10632
drwxr-xr-x 5 jason admin 170B 1 6 23:52 ./
drwxr-xr-x 9 jason admin 306B 1 6 23:52 ../
-rw-r--r-- 1 jason admin 2.9M 1 6 23:52 libmruby.a
-rw-r--r-- 1 jason admin 1.6K 1 6 23:52 libmruby.flags.mak
-rw-r--r-- 1 jason admin 2.3M 1 6 23:52 libmruby_core.a

Start with example/example.go and the cgo linker output from go build -x .; inspect how the example locates mruby/build/host/lib and libmruby.a. Reproduce the build in the reported environment, then verify that the example links and builds successfully without the missing-library error.