OpenJDK fails to build if $A is set to a value with spaces

A DESCRIPTION OF THE PROBLEM :
If the environment variable "A" is set to a value containing spaces, building OpenJDK fails with the error "CompileJavaModules.gmk:594: *** empty variable name. Stop.".

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. export A="AAAA BBBB"
2. ./configure
3. make --warn-undefined-variables (also occurs when this is not set)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
openjdk builds
ACTUAL -
CompileJavaModules.gmk:594: warning: undefined variable 'java.rmi_/sun/rmi/server/ActivationAAAA BBBBctivationSystemImpl_Stub.java'
CompileJavaModules.gmk:594: *** empty variable name. Stop.

CUSTOMER SUBMITTED WORKAROUND :
Unset the "A" variable.

FREQUENCY : always