bug#27142: classpath-0.99-1.e7c13ee0c fails to build

[Ricardo Wurmus <rekado@elephly.net>]

On a machine with 62G memory classpath fails to build from source.

--8<---------------cut here---------------start------------->8---
$ free -h
              total        used        free      shared  buff/cache   available
Mem:            62G        1.1G         35G         32M         25G         61G
Swap:          5.0G          0B        5.0G
--8<---------------cut here---------------end--------------->8---

The problem appears to be that by default the JVM tries to allocate as
much memory as it can, so the initial size of the heap may be larger
than the set maximum.

Here’s the error:

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/gnu/store/ncvpxqykv672wjfygmki7phc7v8kz8iz-ecj-javac-on-jamvm-wrapper-3.2.2/bin/javac  -nowarn -source 1.6 -target 1.6 -bootclasspath '' -classpath ../vm/reference:..:../external/w3c_dom:../external/sax:../external/relaxngDatatype:../external/jsr166:.:: -J-Xmx768M -d . @classes
Minimum heap size greater than max!
touch compile-classes
touch resources
/gnu/store/rw6zb4l1dqg1zx252ri9722ffb1r20jm-fastjar-0.98/bin/fastjar cf glibj.zip gnu java javax org sun META-INF && /gnu/store/rw6zb4l1dqg1zx252ri9722ffb1r20jm-fastjar-0.98/bin/fastjar i glibj.zip
sun: No such file or directory
Error adding sun to jar archive!
make[1]: *** [Makefile:674: glibj.zip] Error 1
make[1]: Leaving directory '/tmp/guix-build-classpath-0.99-1.e7c13ee0c.drv-0/source/lib'
make: *** [Makefile:523: all-recursive] Error 1
phase `build' failed after 3.7 seconds
--8<---------------cut here---------------end--------------->8---

I think we may be able to fix this by ensuring that we also pass
-J-Xms768M to the compiler (or -Xms768M to the invocation of “java”) to
set the initial heap size no greater than the maximum.

--
Ricardo

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