guix: patch gcc 10 with pthreads to remap guix store paths

contrib/guix/manifest.scm

@@ -147,7 +147,10 @@ desirable for building Bitcoin Core release binaries."
                         base-gcc))
 
 (define (make-gcc-with-pthreads gcc)
-  (package-with-extra-configure-variable gcc "--enable-threads" "posix"))
+  (package-with-extra-configure-variable
+    (package-with-extra-patches gcc
+      (search-our-patches "gcc-10-remap-guix-store.patch"))
+    "--enable-threads" "posix"))
 
 (define (make-mingw-w64-cross-gcc cross-gcc)
   (package-with-extra-patches cross-gcc

contrib/guix/patches/gcc-10-remap-guix-store.patch

@@ -0,0 +1,25 @@
+From aad25427e74f387412e8bc9a9d7bbc6c496c792f Mon Sep 17 00:00:00 2001
+From: Andrew Chow <achow101-github@achow101.com>
+Date: Wed, 6 Jul 2022 16:49:41 -0400
+Subject: [PATCH] guix: remap guix store paths to /usr
+
+---
+ libgcc/Makefile.in | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
+index 851e7657d07..476c2becd1c 100644
+--- a/libgcc/Makefile.in
++++ b/libgcc/Makefile.in
+@@ -854,7 +854,7 @@ endif
+ # libgcc_eh.a, only LIB2ADDEH matters.  If we do, only LIB2ADDEHSTATIC and
+ # LIB2ADDEHSHARED matter.  (Usually all three are identical.)
+ 
+-c_flags := -fexceptions
++c_flags := -fexceptions $(shell find /gnu/store -maxdepth 1 -mindepth 1 -type d -exec echo -n " -ffile-prefix-map={}=/usr" \;)
+ 
+ ifeq ($(enable_shared),yes)
+ 
+-- 
+2.37.0
+