fatal error: JavaParser.h: No such file or directory

Hi,

I am trying to build rose on Ubuntu 20.04. I followed the instructions [here](https://github.com/rose-compiler/rose/wiki/Installation-on-Ubuntu-From-Source). I am trying to build with Java support, so I modified the configure command as follows:

```
${ROSE_HOME}/src/configure --prefix=${ROSE_HOME}/install \
--enable-languages=c,c++,java // added java
--with-boost=/usr
--with-boost-libdir=/usr/lib/x86_64-linux-gnu
```

Then we I try to run `make core -j4` in the build directory, I get the following error:

```
/home/ubuntu/Documents/rose/src/src/frontend/ECJ_ROSE_Connection/JavaParserActionROSE.C:22: fatal error: JavaParser.h: No such file or directory
22 | #include "JavaParser.h"
```

I am new to ROSE, so I am sure there is a simple fix here, but I haven't found it yet.

Start with the Ubuntu installation instructions and the configure command enabling Java, then inspect src/frontend/ECJ_ROSE_Connection/JavaParserActionROSE.C around the JavaParser.h include. Reproduce the failure with make core -j4 in the build directory. Done means the Java-enabled build completes without the missing-header error.

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