RFR: [panama foreign] Build tweak to enable build on Windows

[Jorn Vernee]

Hi Henry,

I'm testing out this patch and can confirm jextract.exe is being built, 
but I can't use it to extract a header file.

I'm getting an UnsatisfiedLinkError when loading jclang.dll:

```
PS J:\WS\JNI test\C> jextract Main.h
Exception in thread "main" java.lang.UnsatisfiedLinkError: 
J:\cygwin64\home\Jorn\cygwin-projects\panama\build\windows-x8
6_64-server-release\images\jdk\bin\jclang.dll: %1 is not a valid Win32 
application
         at java.base/java.lang.ClassLoader$NativeLibrary.load0(Native 
Method)
         at 
java.base/java.lang.ClassLoader$NativeLibrary.load(ClassLoader.java:2462)
         at 
java.base/java.lang.ClassLoader$NativeLibrary.loadLibrary(ClassLoader.java:2534)
         at 
java.base/java.lang.ClassLoader.loadLibrary0(ClassLoader.java:2744)
         at 
java.base/java.lang.ClassLoader.loadLibrary(ClassLoader.java:2690)
         at java.base/java.lang.Runtime.loadLibrary0(Runtime.java:851)
         at java.base/java.lang.System.loadLibrary(System.java:1903)
         at 
jdk.internal.clang/jdk.internal.clang.LibClang.<clinit>(LibClang.java:35)
         at 
jdk.jextract/com.sun.tools.jextract.parser.Parser.parse(Parser.java:74)
         at 
jdk.jextract/com.sun.tools.jextract.Context.parse(Context.java:411)
         at 
jdk.jextract/com.sun.tools.jextract.Context.parse(Context.java:387)
         at jdk.jextract/com.sun.tools.jextract.Main.run(Main.java:251)
         at jdk.jextract/com.sun.tools.jextract.Main.main(Main.java:316)
```

When inspecting jclang.dll with 'dependency walker' (a DLL inspection 
tool [1]) it's giving an error about libclang.dll (a dependency of 
jclang.dll), which tells me "No DOS or PE signature found. This file is 
not a valid 32-bit or 64-bit Windows module.". However, when I open the 
original libclang.dll file from my LLVM installation it _is_ being 
recognized as a valid DLL.

I think something is going wrong when copying libclang.dll over? I have 
tried manually copying over the libclang.dll file to the jclang and 
jdk/bin folders, which allows me to extract a header file using that 
command line, but when re-running the build the DLL is being overwritten 
again with the corrupted/invalid version.

Cheers,
Jorn

[1] : http://www.dependencywalker.com/

Henry Jen schreef op 2018-10-26 06:44:
> Hi,
> 
> Please review a web rev[1] that address following,
> 
> 1. Copy the essential share library as recorded by the linker
> following the symbolic link of libclang.so for unix/mac. This leads to
> only one copy of share library instead of a duplicate copy of
> libclang.so. It would be nice to have create libclang as a symbolic
> link, but it’s not needed now.
> 
> This issue is what failed the build when using system provided
> libclang on some systems such as Debian-based Linux distribution.
> After this patch, Debian-based system can be build as described in
> README.foreign.
> 
> 2. Enable build on Windows. This patch allow build image to be
> completed successfully and libclang.dll copied to bin as expected.
> 
> However, this doesn’t mean binder is working on Windows, it’s simply
> get the build going and jextract should be functional. Some test still
> have compiling errors to be fixed, and we don’t have Windows ABI. It’s
> the first step to allow build on Windows.
> 
> I believe a lot of this had been addressed by Jorn, and he actually
> have made more progress on Windows support. Hopefully this is just the
> first step and get Windows going.
> 
> Cheers,
> Henry
> 
> [1] http://cr.openjdk.java.net/~henryjen/panama/build-windows/webrev