jdk build --with-memory-size=1024 broken by JDK-8305100

I've been building --with-jobs=1 --with-memory-size=1024 and that recently started failing with OOME:


```
 Compiling up to 3446 files for java.base
 [stderr] java.util.concurrent.ExecutionException: java.lang.OutOfMemoryError: Java heap space
 [stderr] at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
 [stderr] at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
 [stderr] at javacserver.server.CompilerThreadPool.dispatchCompilation(CompilerThreadPool.java:49)
 [stderr] at javacserver.server.Server.handleRequest(Server.java:211)
 [stderr] at javacserver.server.Server.lambda$start$1(Server.java:173)
 [stderr] at java.base/java.lang.Thread.run(Thread.java:1623)
 [stderr] Caused by: java.lang.OutOfMemoryError: Java heap space
 [stderr] at java.base/java.nio.file.Files.read(Files.java:3213)
 [stderr] at java.base/java.nio.file.Files.readAllBytes(Files.java:3270)
 [stderr] at java.base/jdk.internal.module.ModuleReferences$ExplodedModuleReader.read(ModuleReferences.java:410)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:809)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.findClassInModuleOrNull(BuiltinClassLoader.java:741)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:665)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
 [stderr] at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
 [stderr] at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
 [stderr] at jdk.compiler.interim/com.sun.tools.javac.main.Main.resourceMessage(Main.java:448)
 [stderr] at jdk.compiler.interim/com.sun.tools.javac.main.Main.compile(Main.java:332)
 [stderr] at jdk.compiler.interim/com.sun.tools.javac.main.Main.compile(Main.java:176)
 [stderr] at jdk.compiler.interim/com.sun.tools.javac.main.JavacToolProvider.run(JavacToolProvider.java:54)
 [stderr] at javacserver.server.Server.runCompiler(Server.java:242)
 [stderr] at javacserver.server.CompilerThreadPool.lambda$dispatchCompilation$0(CompilerThreadPool.java:49)
 [stderr] at javacserver.server.CompilerThreadPool$$Lambda$62/0x00000001000c4e98.call(Unknown Source)
 [stderr] at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
 [stderr] at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
 [stderr] at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
 [stderr] at java.base/java.lang.Thread.runWith(Thread.java:1636)
 [stderr] ... 1 more
 gmake[3]: *** [CompileJavaModules.gmk:95: /home/martin/ws/jdk/build/linux-x86_64-server-release/jdk/modules/java.base/_the.java.base_batch] Error 1
 gmake[2]: *** [make/Main.gmk:193: java.base-java] Error 2

 ERROR: Build failed for target 'images' in configuration 'linux-x86_64-server-release' (exit code 2)
 Stopping javac server

 === Output from failing command(s) repeated here ===
 * For target jdk_modules_java.base__the.java.base_batch:
 [stderr] java.util.concurrent.ExecutionException: java.lang.OutOfMemoryError: Java heap space
 [stderr] at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
 [stderr] at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
 [stderr] at javacserver.server.CompilerThreadPool.dispatchCompilation(CompilerThreadPool.java:49)
 [stderr] at javacserver.server.Server.handleRequest(Server.java:211)
 [stderr] at javacserver.server.Server.lambda$start$1(Server.java:173)
 [stderr] at java.base/java.lang.Thread.run(Thread.java:1623)
 [stderr] Caused by: java.lang.OutOfMemoryError: Java heap space
 [stderr] at java.base/java.nio.file.Files.read(Files.java:3213)
 [stderr] at java.base/java.nio.file.Files.readAllBytes(Files.java:3270)
 [stderr] at java.base/jdk.internal.module.ModuleReferences$ExplodedModuleReader.read(ModuleReferences.java:410)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:809)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.findClassInModuleOrNull(BuiltinClassLoader.java:741)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:665)
 [stderr] at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
    ... (rest of output omitted)
```