RFR: 8269131: Update libxml2 to version 2.9.12 [v2]

[Ambarish Rapte]

On Thu, 1 Jul 2021 23:20:51 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Ambarish Rapte has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   changes as per review
>
> modules/javafx.web/src/main/native/Source/ThirdParty/libxml/UPDATING.txt line 3:
> 
>> 1: Updating libxml in OpenJFX:
>> 2: 
>> 3: 1. Download respective libxml source tarball from here: http://xmlsoft.org/sources
> 
> As an alternative, the source can be downloaded by cloning:
> https://gitlab.gnome.org/GNOME/libxml2.git
> They tag each release. Maybe it isn't worth noting here.

Added the git url also as an alternate source in the steps.

> modules/javafx.web/src/main/native/Source/ThirdParty/libxml/UPDATING.txt line 18:
> 
>> 16: 
>> 17: 5. Remove files & directories which are not relevant to JavaFX WebKit.
>> 18:    Use git clean command. (git clean -df modules/)
> 
> This presumes everything that isn't already tracked is unwanted. If they ever add a new file (e.g., a new utility) that is referenced by methods in existing files, the build would fail.

I removed the use of git clean command from the steps.

> modules/javafx.web/src/main/native/Source/ThirdParty/libxml/UPDATING.txt line 43:
> 
>> 41:     > find src/ -name "*.h" -type f -exec bash -c 'expand -t 4 "$0" | sponge "$0"' {} \;
>> 42: 7.3 Remove trailing whitespaces:
>> 43:     > find . -type f -exec sed -i '' 's/[[:space:]]\{1,\}$//' {} \+
> 
> Can you check whether this has caused any problems with the non-source files (e.g., the Makefiles)? It might be safer to just do this on the same set of files for which you expand tabs. See my comment on the `Makefile.am` file.

`Makefile.am` tab expansion was a result of running a wrong command, but not this. Also I changed this command to remove trailing whitespaces only from source files.

> modules/javafx.web/src/main/native/Source/ThirdParty/libxml/src/Makefile.am line 49:
> 
>> 47: 
>> 48: libxml2_la_SOURCES = SAX.c entities.c encoding.c error.c parserInternals.c  \
>> 49:         parser.c tree.c hash.c list.c xmlIO.c xmlmemory.c uri.c  \
> 
> It looks like this file has had its tabs expanded which is not what we want for a `Makefile` (only for source files, as you noted in `UPDATING.txt`).

I think I ran a wrong command to cause this, It is corrected now.

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PR: https://git.openjdk.java.net/jfx/pull/562