RFR: JDK-8056053: Disable HOTSPOT_BUILD_JOBS when building with configure

[Erik Joelsson]

Hello,

Please review this proposed fix for the Hotspot build.

In the new jdk9 build, we utilize the gnu make job server, which 
automatically makes sure the -j flag gets propagated and shared between 
all recursive make calls. In the hotspot build, this gets overridden by 
the HOTSPOT_BUILD_JOBS variable. Configure estimates a reasonable number 
of parallel make jobs into the JOBS variable, which gets propagated to 
the HOTSPOT_BUILD_JOBS variable. This used to work well enough, but in 
the new build, the hotspot build is happening concurrently with other 
parts of the build and the consequence is that the hotspot build gets 
JOBS number of jobs and the rest of the build also gets JOBS number of 
jobs, all of which are used at the same time. We would like the whole 
build to share in the same job pool.

To fix this, the setting of -j$(HOTSPOT_BUILD_JOBS) needs to be made 
conditional and we need to add .NOTPARALLEL: to a number of makefiles in 
hotspot that currently can't handle being executed in parallel. Lastly, 
the + sign must be added first to recipe lines that call make 
recursively but are not explicitly using the MAKE variable directly. The 
result will be that the active -j flag in the root makefiles will just 
automatically propagate down to the hotspot makefiles.

Bug: https://bugs.openjdk.java.net/browse/JDK-8056053
Webrev: http://cr.openjdk.java.net/~erikj/8056053/webrev.01/

/Erik