Fix bootclasspath string initialization

When running the runtime with an image without explicitly specifying
the bootclasspath (with the -Xbootclasspath option), we construct it
from the location of DEX files loaded from the image.

This allows to fix the JDWP test ClassPathsTest#testClassPaths001 on
the host where the bootclasspath is not explicitly specified on the
command line.

Bug: 18812378
Change-Id: I726eafd8b9e59dc9513beeb7082cf086fe89c4b1
2 files changed