Windows pre-built 16.1.2 can't load compiler

Running the following code fails with unmodified install:

(ext:install-c-compiler)

Error message:

;;; Loading #P"C:/Program Files (x86)/ECL/cmp.fas"

Condition of type: SIMPLE-ERROR
LOAD: Could not load file #P"C:/Program Files (x86)/ECL/cmp.fas" (Error: "The operation completed successfully.
")

Appears to be a file permissions issue, but granting more file permissions and installing to somewhere other than the default of C:\Program Files (x86)\ECL gave the same result. Confirmed that is the correct path and the file is accessible by the current user from the prompt.

Observed on 2 separate machines running Windows 10 Pro 64-bit with the 16.1.2 installer found on the ECL project files page.

Building the same version of ECL from source using MSVC on Windows does not result in this error.