$ opam switch -vv create test ocaml-variants.4.07.1+fp
+ /home/tgphelps/.local/bin/ocamlc "-vnum"
- 4.07.1

<><> Gathering sources ><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ocaml-variants.4.07.1+fp] found in cache
+ /bin/tar "xfz" "/home/tgphelps/.opam/download-cache/md5/35/352fe8d46cb238a26aa10c38bad6ecb6" "-C" "/tmp/opam-33287-ccabea"

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+ /home/tgphelps/.opam/opam-init/hooks/sandbox.sh "build" "./configure" "-prefix" "/home/tgphelps/.opam/test" "-with-debug-runtime" "-with-frame-pointers" (CWD=/home/tgphelps/.opam/test/.opam-switch/build/ocaml-variants.4.07.1+fp)
- Configuring OCaml version 4.07.1
- Configuring for host x86_64-unknown-linux-gnu ...
- Configuring for target x86_64-unknown-linux-gnu ...
- Using compiler gcc.
- gcc: error trying to exec 'cc1': execvp: No such file or directory
- Compiler family and version: .
- [ERROR!] Unable to compile the test program.
-  Make sure the C compiler gcc is properly installed.
[ERROR] The compilation of ocaml-variants failed at
        "/home/tgphelps/.opam/opam-init/hooks/sandbox.sh build ./configure
        -prefix /home/tgphelps/.opam/test -with-debug-runtime
        -with-frame-pointers".
∗ installed base-bigarray.base
∗ installed base-threads.base
∗ installed base-unix.base

#=== ERROR while compiling ocaml-variants.4.07.1+fp ===========================#
# context     2.0.0 | linux/x86_64 |  | https://opam.ocaml.org#9ecbe4e1
# path        ~/.opam/test/.opam-switch/build/ocaml-variants.4.07.1+fp
# command     ~/.opam/opam-init/hooks/sandbox.sh build ./configure -prefix /home/tgphelps/.opam/test -with-debug-runtime -with-frame-pointers
# exit-code   2
# env-file    ~/.opam/log/ocaml-variants-33287-05296d.env
# output-file ~/.opam/log/ocaml-variants-33287-05296d.out
### output ###
# Configuring OCaml version 4.07.1
# Configuring for host x86_64-unknown-linux-gnu ...
# Configuring for target x86_64-unknown-linux-gnu ...
# Using compiler gcc.
# gcc: error trying to exec 'cc1': execvp: No such file or directory
# Compiler family and version: .
# [ERROR!] Unable to compile the test program.
#  Make sure the C compiler gcc is properly installed.



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions were aborted
│ ∗ install ocaml 4.07.1
└─
┌─ The following actions failed
│ λ build ocaml-variants 4.07.1+fp
└─
┌─ The following changes have been performed (the rest was aborted)
│ ∗ install base-bigarray base
│ ∗ install base-threads  base
│ ∗ install base-unix     base
└─
Switch initialisation failed: clean up? ('n' will leave the switch partially
installed) [Y/n] y
'opam switch -vv create test ocaml-variants.4.07.1+fp' failed.