RFR: 8264874: Build interim-langtools for HotSpot only if Graal is enabled

[Ioi Lam]

Many HotSpot developers make only the `hotspot` target, and copy the resulting `libjvm.so` into an already-build JDK image.

HotSpot requires `interim-langtools` only when Graal is enabled. When Graal is disabled, we can avoid building `interim-langtools`. This improves the build time of `make hotspot` by about 20 seconds, or about 15%:

Old:
$ make clean
$ time make hotspot
....
real 1m57.905s
user 42m22.524s
sys 3m7.372s

New:
$ make clean
$ time make hotspot
....
real 1m39.916s
user 41m59.984s
sys 3m3.188s

-------------

Commit messages:
 - 8264874: Build interim-langtools for HotSpot only if Graal is enabled

Changes: https://git.openjdk.java.net/jdk/pull/3389/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3389&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264874
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3389.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3389/head:pull/3389

PR: https://git.openjdk.java.net/jdk/pull/3389