Install a Go binary, keep dependencies / packages - go

Question

When I build a Go binary, I usually do something like this:
go build -ldflags "-X main.basedir somevar" -o mybuilddir/bin/myfile mypackage/main"
this builds the binary and places it in a custom directory. But this doesn't keep the "intermediate" package files beneath pkg/, which would speed up the next compilation runs.
The solution would be go install, but I cannot specify an output directory. It seems to be possible to set the binary directory with GOBIN, but I am unable to specify the name of the executable (always main).
What is a possible solution to this problem?
Custom destionation directory
Custom name (not main)
Keep intermediate generated package files (.a)
This is the src directory of GOPATH:
GOPATH/src$ tree
.
└── mypackage
├── packagea
│   └── packagea.go
├── packageb
│   └── packageb.go
└── main
   └── mypackage.go
With go install, the package files (.a) are created in $GOPATH/pkg, with go build, I can't find the .a files anywhere.

Answer 1

Update Nov. 2017: Go 1.10 (Q1 2018) will add caching for go build and go install: see "go build rebuilds unnecessarily".
Original answer (2014)
With go install, the package files (.a) are created in $GOPATH/pkg, with go build, I can't find the .a files anywhere.
As mentioned in "How does the go build command work ?"
The final step is to pack the object file into an archive file, .a, which the linker and the compiler consume.
Because we invoked go build on a package, the result is discarded as $WORK is deleted after the build completes.
If we invoke go install -x two additional lines appear in the output
mkdir -p /home/dfc/go/pkg/linux_arm/crypto/
cp $WORK/crypto/hmac.a /home/dfc/go/pkg/linux_arm/crypto/hmac.a
This demonstrates the difference between go build and install;
build builds,
install builds then installs the result to be used by other builds.