Can I make gotest pass compiler flags?

I have just put together a Go package that is going to be a part in a fairly large system with a lot of shared packages. I was able to get it to compile by writing its Makefile such that the compiler is called with -I flags:

include $(GOROOT)/src/Make.inc

TARG=foobar
GOFILES=\
    foobar.go\

foobar:
    $(GC) -I$(CURDIR)/../intmath -I$(CURDIR)/../randnum foobar.go

include $(GOROOT)/src/Make.pkg

It compiles just fine, and being a good boy, I wrote a comprehensive set of tests. However, when I try to run the tests with gotest, I get a compile error:

$ gotest
rm -f _test/foobar.a
8g  -o _gotest_.8 foobar.go  foobar_test.go
foobar.go:4: can't find import: intmath
make: *** [_gotest_.8] Error 1
gotest: "C:\\msys\\bin\\sh.exe -c \"gomake\" \"testpackage\" \"GOTESTFILES=foobar_test.go\"" failed: exit status 2

So, the Go file itself will compile when I use the -I flags to tell it where to find the intmath and randnum packages, but gotest doesn't seem to use the Makefile.

Answering peterSO's question:
foobar.go's import section looks like this:

import (
    "intmath"
    "randnum"
    "container/vector"
)

And the compile works fine as long as I have the -I flags going to the compiler. I have tried to use relative paths, like this:

import (
    "../intmath"
    "../randnum"
    "container/vector"
)

but that just doesn't seem to work.

EDIT: answering further peterSO questions:

GOROOT is set to C:\Go the directory where I have all of the Go stuff -- aside from my source code -- installed. I was expecting the relative path to be relative to the directory in which the source file lives.

My source tree looks like this:

server/
    foobar/
    randnum/
    intmath/

So, while I am open to a different, more Go-idiomatic directory structure, my instinct is to arrange them as peers.

Is there some way that I can nudge gotest into compiling foobar.go with the needed flags?

Create the Windows source code directory structure:

C:\server
C:\server\foobar
C:\server\intnum

For intnum.go:

package intnum

func IntNum() int {
	return 42
}

Makefile:

include $(GOROOT)/src/Make.inc
TARG=server/intnum
GOFILES=\
	intnum.go\
include $(GOROOT)/src/Make.pkg

Run:

$ cd c/server/intnum
$ make install

For foobar.go:

package foobar

import (
	"math"
	"server/intnum"
)

func FooBar() float64 {
	return float64(intnum.IntNum()) * math.Pi
}

Makefile:

include $(GOROOT)/src/Make.inc
TARG=server/foobar
GOFILES=\
	foobar.go\
include $(GOROOT)/src/Make.pkg

Run:

$ cd /c/server/foobar
$ make install

After the install, the intnum.a and foobar.a package files will be in the $GOROOT\pkg\windows_386\server (C:\Go\pkg\windows_386\server) directory`.