Enable ZSTD support properly for Android

In #28766 (moved) we tried to enable ZSTD support for Android but just specifying --enable-zstd when compiling tor and extracting the library is not enough:

WARNING: Unable to find libzstd, install pkg-config, and check the PKG_CONFIG_PATH environment variable, or set ZSTD_CFLAGS and ZSTD_LIBS

added GeorgKoppen202005 TorBrowserTeam202005R component::applications/tor browser owner::gk priority::medium resolution::fixed severity::normal status::closed tbb-10.0a1 tbb-rbm type::defect labels

We have at least two options to fix that:

1. Installing pkg-config and pointing it to /var/tmp/dist/zstd/lib/pkgconfig
2. Setting ZSTD_CFLAGS and ZSTD_LIBS properly.

I opted for 2) as 1) needs pkg-config installed (presumable for all other platforms as well if we want to keep the container amount low) and we end up with -L/var/tmp/dist/zstd/lib -lzstd for ld which is not really needed. Pointing directly to the static lib we want to have used should be enough if I understand things correctly.

bug_34219 (https://gitweb.torproject.org/user/gk/tor-browser-build.git/commit/?h=bug_34219&id=40809c54c2e198cbe11d0d4f19bc9fd7c242166b) has a patch for review.

It still needs some testing.

Trac:
Keywords: TorBrowserTeam202005 deleted, TorBrowserTeam202005R added
Status: assigned to needs_review

Okay, it compiles for all architecture and the armv7 even runs. So, good for review I think. Here is the build I tested:

https://people.torproject.org/~gk/testbuilds/tor-browser-testbuild-34219-android-armv7-multi-qa.apk https://people.torproject.org/~gk/testbuilds/tor-browser-testbuild-34219-android-armv7-multi-qa.apk.asc

Looks good to me. Thanks!

(top is from 9.5a13)

Tor version 0.4.3.5 (git-5ceb60e5ca61fec9). 
Library versions	Compiled		Runtime
Libevent		2.1.11-stable  		2.1.11-stable
OpenSSL 		1.1.1g         		1.1.1g
Zlib    		1.2.11         		1.2.11

Tor version 0.4.3.5 (git-5ceb60e5ca61fec9). 
Library versions	Compiled		Runtime
Libevent		2.1.11-stable  		2.1.11-stable
OpenSSL 		1.1.1g         		1.1.1g
Zlib    		1.2.11         		1.2.11
Libzstd 		1.4.4          		1.4.4

Merged onto master with commit ede6ffb414a8684f5dab8615836504acf2774734.

Trac:
Keywords: N/A deleted, tbb-10.0a1 added
Resolution: N/A to fixed
Status: needs_review to closed

closed

moved to tpo/applications/tor-browser#34219 (closed)