cgo build fail

make.txt

$ go build -x
WORK=/tmp/go-build407974663
mkdir -p $WORK/github.com/kortschak/boom/_obj/
cd /home/daniel/Development/src/github.com/kortschak/boom
/usr/local/src/go/pkg/tool/linux_amd64/cgo -objdir $WORK/github.com/kortschak/boom/_obj/ -- -g -O2 -fPIC -m64 -pthread -I $WORK/github.com/kortschak/boom/_obj/ boom.go
/usr/local/src/go/pkg/tool/linux_amd64/6c -FVw -I $WORK/github.com/kortschak/boom/_obj/ -I /usr/local/src/go/pkg/linux_amd64 -o $WORK/github.com/kortschak/boom/_obj/_cgo_defun.6 -DGOOS_linux -DGOARCH_amd64 $WORK/github.com/kortschak/boom/_obj/_cgo_defun.c
gcc -I . -g -O2 -fPIC -m64 -pthread -g -O2 -fPIC -m64 -pthread -I $WORK/github.com/kortschak/boom/_obj/ -o $WORK/github.com/kortschak/boom/_obj/_cgo_main.o -c $WORK/github.com/kortschak/boom/_obj/_cgo_main.c
gcc -I . -g -O2 -fPIC -m64 -pthread -g -O2 -fPIC -m64 -pthread -I $WORK/github.com/kortschak/boom/_obj/ -o $WORK/github.com/kortschak/boom/_obj/_cgo_export.o -c $WORK/github.com/kortschak/boom/_obj/_cgo_export.c
gcc -I . -g -O2 -fPIC -m64 -pthread -g -O2 -fPIC -m64 -pthread -I $WORK/github.com/kortschak/boom/_obj/ -o $WORK/github.com/kortschak/boom/_obj/boom.cgo2.o -c $WORK/github.com/kortschak/boom/_obj/boom.cgo2.c
gcc -I . -g -O2 -fPIC -m64 -pthread -o $WORK/github.com/kortschak/boom/_obj/_cgo_.o $WORK/github.com/kortschak/boom/_obj/_cgo_main.o $WORK/github.com/kortschak/boom/_obj/_cgo_export.o $WORK/github.com/kortschak/boom/_obj/boom.cgo2.o -L. -lbam -lz
/usr/local/src/go/pkg/tool/linux_amd64/cgo -objdir $WORK/github.com/kortschak/boom/_obj/ -dynimport $WORK/github.com/kortschak/boom/_obj/_cgo_.o -dynout $WORK/github.com/kortschak/boom/_obj/_cgo_import.c
/usr/local/src/go/pkg/tool/linux_amd64/6c -FVw -I $WORK/github.com/kortschak/boom/_obj/ -I /usr/local/src/go/pkg/linux_amd64 -o $WORK/github.com/kortschak/boom/_obj/_cgo_import.6 -DGOOS_linux -DGOARCH_amd64 $WORK/github.com/kortschak/boom/_obj/_cgo_import.c
/usr/local/src/go/pkg/tool/linux_amd64/6g -o $WORK/github.com/kortschak/boom/_obj/_go_.6 -p github.com/kortschak/boom -D _/home/daniel/Development/src/github.com/kortschak/boom -I $WORK ./bam.go ./header.go ./record.go ./sam.go $WORK/github.com/kortschak/boom/_obj/_cgo_gotypes.go $WORK/github.com/kortschak/boom/_obj/boom.cgo1.go
/usr/local/src/go/pkg/tool/linux_amd64/pack grc $WORK/github.com/kortschak/boom.a $WORK/github.com/kortschak/boom/_obj/_go_.6 $WORK/github.com/kortschak/boom/_obj/_cgo_import.6 $WORK/github.com/kortschak/boom/_obj/_cgo_defun.6 $WORK/github.com/kortschak/boom/_obj/_cgo_export.o $WORK/github.com/kortschak/boom/_obj/boom.cgo2.o
mkdir -p $WORK/github.com/kortschak/boom/examples/samtest/_obj/
cd /home/daniel/Development/src/github.com/kortschak/boom/examples/samtest
/usr/local/src/go/pkg/tool/linux_amd64/6g -o $WORK/github.com/kortschak/boom/examples/samtest/_obj/_go_.6 -p github.com/kortschak/boom/examples/samtest -D _/home/daniel/Development/src/github.com/kortschak/boom/examples/samtest -I $WORK -I /home/daniel/Development/pkg/linux_amd64 ./samtest.go
/usr/local/src/go/pkg/tool/linux_amd64/pack grc $WORK/github.com/kortschak/boom/examples/samtest.a $WORK/github.com/kortschak/boom/examples/samtest/_obj/_go_.6
cd .
/usr/local/src/go/pkg/tool/linux_amd64/6l -o $WORK/github.com/kortschak/boom/examples/samtest/_obj/a.out -L $WORK -L /home/daniel/Development/pkg/linux_amd64 $WORK/github.com/kortschak/boom/examples/samtest.a
# github.com/kortschak/boom/examples/samtest
github.com/kortschak/boom.(*textHeader).header: undefined: github.com/kortschak/boom.textHeader.header
bam_fetch(0): not defined
samclose(0): not defined
bam_index_destroy(0): not defined
samread(0): not defined
samwrite(0): not defined
samopen(0): not defined
bam_index_build(0): not defined
bam_index_load(0): not defined