Disable all JIT

[Kudo]

Summary

As facebook/react-native#24261, the community report my experimented builds still have crashes.

1. w/o DFG JIT
2. w/ DFG JIT and fix __clear_cache issue.
3. w/o DFG JIT and fix __clear_cache issue.
   (fix __clear_cache commit as here Kudo@daf5700)

And they did mention that the no_jit version is crash free.
I am going to propose turning off JIT totally to make sure at least we have a stable JSC.
Will re-enable JIT if community feedback for a lot performance dropping and will try for next major WebKitWPE major release.

Disable JIT brings two benefits:

1. Binary size reducing about 1MB
2. Memory save about 48%

Measurement

Measurement methodology is pretty much like what I did in #105
For memory profiling, it is to execute adb shell dumpsys meminfo com.javascriptcore.profiler and compare TOTAL memory usage right after sunspider, jetstream, octane2, sixspeed benchmarks.

Results

Npm Version	Publish Date	Config	WebkitGTK Revision	WebkitGTK Date	TTI	SunSpider	Jetstream Hashmap	Octane2	SixSpeed	Render Flat	Render Deep	Size	Memory
241213.1.0	2019-04-30	webkitGTK:2.22.6 chromiumICUCommit:b34251f i18n:false	241213	2019-02-08	456	469	557	1569	416	436	347	7.6/10.0	162525
174650.0.2	-	Stock RN58 (non-i18n)	174650	2014-10-13	454	568	4005	1996	1454	518	395	2.7 (with libicu_common.so)	169026
@kudo-ci/jsc-android@241213-no-dfg-jit	2019-05-17	webkitGTK:2.22.6 chromiumICUCommit:b34251f i18n:false DFG_JIT:false	241213	2018-09-21	451	534	3033	1780	420	510	430	6.3/8.0	146165
@kudo-ci/jsc-android@241213-no-jit	2019-05-17	webkitGTK:2.22.6 chromiumICUCommit:b34251f i18n:false DFG_JIT:false JIT:false	241213	2018-09-21	456	1947	11799	5887	973	538	431	5.0/7.1	70385

https://docs.google.com/spreadsheets/d/1hqX3ai-NCpN_J6YQDTKnKNBctWnMFA6EyOdVhPvwUas/edit#gid=193471288

[newyankeecodeshop]

According to your benchmarks, disabling JIT completely really destroys performance. Worse than the original JSC from 2014.
Maybe the answer is for folks that experience the crashing to switch to a different version of JSC, or a build without JIT? But disabling it for the entire community looks like it will cause major performance regressions.

[Kudo]

I think that is for benchmark. For a normal RN app, the renderflat and renderdeep are more like real world use case.
Someone even said that no-jit JSC is faster than stock RN058.
My opinion is to disable JIT first and make sure it will not crash.
If a user really wants JIT, we could have another build variant like what we did for Intl version later. (And use with crash risk)

[kmagiera]

Let's get this in and publish to NPM for other people to try