Internet Explorer prod build broken at runtime by 8.3.20 upgrade

[Wisdomb33r]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes, the previous version in which this bug was not present was: 8.3.19

Description

Production build is completely fine when compiled with 8.3.19 and is working on Internet Explorer. Upgrading to 8.3.20 (and devkit/build-angular to 0.803.20 accordingly) is breaking the runtime execution of the app. No other project change besides this 19-to-20 change.

🔬 Minimal Reproduction

The problem is NOT present when I use ng serve nor it is with ng serve --prod (assuming here the target is es5). I could only get the error when the final prod build is deployed on a web server (with differential loading active). The error stacktrace is consequently lost in the minified JS and doesn't say much about the problem location.

🔥 Exception or Error

Object doesn't support property or method 'some'

According to MDN, Arrays.some is supported by Internet Explorer since version 9. I searched my entire code for calls to any some method and could not find a single one.

🌍 Your Environment

Angular CLI: 8.3.20
Node: 12.13.1
OS: win32 x64
Angular: 8.2.14
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.803.20
@angular-devkit/build-angular      0.803.20
@angular-devkit/build-optimizer    0.803.20
@angular-devkit/build-webpack      0.803.20
@angular-devkit/core               8.3.20
@angular-devkit/schematics         8.3.20
@angular/cdk                       8.2.3
@angular/cli                       8.3.20
@angular/material                  8.2.3
@angular/material-moment-adapter   8.2.3
@ngtools/webpack                   8.3.20
@schematics/angular                8.3.20
@schematics/update                 0.803.20
rxjs                               6.5.3
typescript                         3.5.3
webpack                            4.39.2

Anything else relevant?
IE11

Browserslist :

> 0.5%
last 2 versions
Firefox ESR
not dead
IE 9-11 # For IE 9-11 support, remove 'not'.

Compiler options for ng build --prod :
module : exnext
target: es2015

[clydin]

Duplicate of #16366

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