I downloaded Cesium-1.18 onto a RedHat 6 box. I did an unzip of the file. The ownership of permissions of many of the files was bad:
unzip Cesium\-1\.18\.zip
\.\.\.
ls -al
total 38892
drwxr-xr-x. 7 jeffrey.hines group-1 4096 Feb 5 16:01 .
drwxr-xr-x. 6 jeffrey.hines group-1 4096 Feb 5 16:07 ..
drwxr-xr-x. 6 jeffrey.hines group-1 4096 Feb 5 16:01 Apps
drwxr-xr-x. 5 jeffrey.hines group-1 4096 Feb 5 16:01 Build
-rw-r--r--. 1 jeffrey.hines group-1 39239630 Feb 5 16:00 Cesium-1.18.zip
-rw-rw-rw-. 1 jeffrey.hines group-1 198008 Feb 1 13:23 CHANGES.md
...
$ ls -al Build
total 36
drwxr-xr-x. 5 jeffrey.hines group-1 4096 Feb 5 16:01 .
drwxr-xr-x. 7 jeffrey.hines group-1 4096 Feb 5 16:01 ..
drw-rw-rw-. 6 jeffrey.hines group-1 4096 Feb 1 13:36 Cesium
drw-rw-rw-. 6 jeffrey.hines group-1 4096 Feb 1 13:36 CesiumUnminified
drw-rw-rw-. 7 jeffrey.hines group-1 20480 Feb 1 13:33 Documentation
###--> Notice that these directories don't have executable permission
$ ls -al Build/Cesium
ls: cannot access Build/Cesium/.: Permission denied
ls: cannot access Build/Cesium/…: Permission denied
ls: cannot access Build/Cesium/Assets: Permission denied
ls: cannot access Build/Cesium/Cesium.js: Permission denied
ls: cannot access Build/Cesium/ThirdParty: Permission denied
ls: cannot access Build/Cesium/Widgets: Permission denied
ls: cannot access Build/Cesium/Workers: Permission denied
total 0
d??? ? ? ? ? ? .
d??? ? ? ? ? ? …
d??? ? ? ? ? ? Assets
-??? ? ? ? ? ? Cesium.js
d??? ? ? ? ? ? ThirdParty
d??? ? ? ? ? ? Widgets
d??? ? ? ? ? ? Workers