Turns out this was an issue with Boost 1.75 (which I had patched over from core-updates, requiring the C++20 support). I feel like I might as well post the simple Folly version bump here and the core-updates Boost patch in the following reply. Not sure when core-updates will be merged or if Boost 1.76 will be out by then.
From 334fc83ae2a3d92ba7813150709532b252592817 Mon Sep 17 00:00:00 2001
Date: Thu, 7 Jan 2021 21:54:37 +0000
Subject: [PATCH] gnu: folly: Update to 2021.01.25.00.
* gnu/packages/cpp.scm (folly): Update to 2021.01.25.00.
---
gnu/packages/cpp.scm | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/gnu/packages/cpp.scm b/gnu/packages/cpp.scm
index ca8f7a9f80..73a3ceb2df 100644
--- a/gnu/packages/cpp.scm
+++ b/gnu/packages/cpp.scm
@@ -14,7 +14,7 @@
;;;
;;; This file is part of GNU Guix.
@@ -689,7 +689,7 @@ standard GNU style syntax for options.")
(define-public folly
(package
(name "folly")
- (version "2020.10.05.00")
+ (version "2021.01.25.00")
(source (origin
(method git-fetch)
(uri (git-reference
@@ -698,7 +698,7 @@ standard GNU style syntax for options.")
(file-name (git-file-name name version))
(sha256
(base32
- "0q4w4cvjxffc462hvs8h4zryq4965j7015zvkwagcm6cj6wmz3cn"))))
+ "14dl1g6vf7mc90mcync5h2lp14fwcx8n9h91pmiq6rfgv1fjjrwz"))))
(build-system cmake-build-system)
(arguments
'(;; Tests must be explicitly enabled
--
2.30.0