Here's a relevant part of 'tests/guix-package.log':

++ guix build -e '(@@ (gnu packages base) gnu-make-boot0)'
accepted connection from pid 30852, uid 1000
+ boot_make_drv='/home/tester/guix-test2/test-tmp/store/05bmw6n7vw80s111qd1rghs2rgz3g211-make-boot0-3.82-debug
/home/tester/guix-test2/test-tmp/store/ngpnqr5mdxi8n7pnv7c12g644bw1syy8-make-boot0-3.82'
51 operations
+ guix package --bootstrap -p t-profile-30830 -i '/home/tester/guix-test2/test-tmp/store/05bmw6n7vw80s111qd1rghs2rgz3g211-make-boot0-3.82-debug
/home/tester/guix-test2/test-tmp/store/ngpnqr5mdxi8n7pnv7c12g644bw1syy8-make-boot0-3.82'
accepted connection from pid 30858, uid 1000
The following package will be installed:
   make-boot0-3.82	#f	/home/tester/guix-test2/test-tmp/store/05bmw6n7vw80s111qd1rghs2rgz3g211-make-boot0-3.82-debug
/home/tester/guix-test2/test-tmp/store/ngpnqr5mdxi8n7pnv7c12g644bw1syy8-make-boot0-3.82

error processing client input: path `/home/tester/guix-test2/test-tmp/store/05bmw6n7vw80s111qd1rghs2rgz3g211-make-boot0-3.82-debug
/home/tester/guix-test2/test-tmp/store/ngpnqr5mdxi8n7pnv7c12g644bw1syy8-make-boot0-3.82' is not in the Nix store
11 operations
guix package: error: build failed: path `/home/tester/guix-test2/test-tmp/store/05bmw6n7vw80s111qd1rghs2rgz3g211-make-boot0-3.82-debug
/home/tester/guix-test2/test-tmp/store/ngpnqr5mdxi8n7pnv7c12g644bw1syy8-make-boot0-3.82' is not in the Nix store