bug#57005: PETSc is not reproducible

["Ludovic Courtès" <ludovic.courtes@inria.fr>]

PETSc 3.16.1 is not reproducible as it captures the kernel version and
number of processors of the machine it’s built on:

--8<---------------cut here---------------start------------->8---
$ guix describe
Generation 223	Aug 01 2022 00:30:24	(current)
  guix ab59155
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: ab59155c5a38dda7efaceb47c7528578fcf0def4
$ guix challenge petsc --diff="$(type -P diff) -ru"
/gnu/store/4dii69ddwxjiyf2pnay82l4w64s03n60-petsc-3.16.1 contents differ:
  no local build for '/gnu/store/4dii69ddwxjiyf2pnay82l4w64s03n60-petsc-3.16.1'
  https://ci.guix.gnu.org/nar/lzip/4dii69ddwxjiyf2pnay82l4w64s03n60-petsc-3.16.1: 1fqg24x0qq0vww8a21a4ifyxlwy0l7bg8zzrzvg024lk76n54kxh
  https://bordeaux.guix.gnu.org/nar/lzip/4dii69ddwxjiyf2pnay82l4w64s03n60-petsc-3.16.1: 162fp2wsxxjjl1pd42522jb3i37hpq8lnfs12qaipzhkzqda5h34
 bordeaux.guix.gnu.org  10.3MiB                                                                                                                      9.7MiB/s 00:01 [##################] 100.0%diff -ru /tmp/guix-directory.4kiUDI/include/petscmachineinfo.h /tmp/guix-directory.0i2wFi/include/petscmachineinfo.h
--- /tmp/guix-directory.4kiUDI/include/petscmachineinfo.h	1970-01-01 01:00:01.000000000 +0100
+++ /tmp/guix-directory.0i2wFi/include/petscmachineinfo.h	1970-01-01 01:00:01.000000000 +0100
@@ -1,6 +1,6 @@
 static const char *petscmachineinfo = "\n"
 "-----------------------------------------\n"
-"Machine characteristics: Linux-5.15.10-gnu-x86_64-with-glibc2.33\n"
+"Machine characteristics: Linux-5.15.11-gnu-x86_64-with-glibc2.33\n"
 "Using PETSc directory: /gnu/store/4dii69ddwxjiyf2pnay82l4w64s03n60-petsc-3.16.1\n"
 "Using PETSc arch: \n"
 "-----------------------------------------\n";
Binary files /tmp/guix-directory.4kiUDI/lib/libpetsc.so and /tmp/guix-directory.0i2wFi/lib/libpetsc.so differ
Binary files /tmp/guix-directory.4kiUDI/lib/libpetsc.so.3.16 and /tmp/guix-directory.0i2wFi/lib/libpetsc.so.3.16 differ
Binary files /tmp/guix-directory.4kiUDI/lib/libpetsc.so.3.16.1 and /tmp/guix-directory.0i2wFi/lib/libpetsc.so.3.16.1 differ
diff -ru /tmp/guix-directory.4kiUDI/lib/petsc/conf/petscvariables /tmp/guix-directory.0i2wFi/lib/petsc/conf/petscvariables
--- /tmp/guix-directory.4kiUDI/lib/petsc/conf/petscvariables	1970-01-01 01:00:01.000000000 +0100
+++ /tmp/guix-directory.0i2wFi/lib/petsc/conf/petscvariables	1970-01-01 01:00:01.000000000 +0100
@@ -107,10 +107,10 @@
 OMAKE_PRINTDIR  = /gnu/store/55cbpsi18mahg131nmiya6km5b4mscfa-make-4.3/bin/make  --print-directory
 OMAKE = /gnu/store/55cbpsi18mahg131nmiya6km5b4mscfa-make-4.3/bin/make  --no-print-directory
 MAKE_PAR_OUT_FLG = --output-sync=recurse
-MAKE_NP = 40
-MAKE_TEST_NP = 40
-MAKE_LOAD = 96.0
-NPMAX = 64
+MAKE_NP = 24
+MAKE_TEST_NP = 24
+MAKE_LOAD = 48.0
+NPMAX = 32
 SONAME_FUNCTION = $(1).$(SL_LINKER_SUFFIX).$(2)
 SL_LINKER_FUNCTION =  -shared  -fPIC -Wall -Wwrite-strings -Wno-strict-aliasing -Wno-unknown-pragmas -fstack-protector -fvisibility=hidden -g3 -O0 -Wl,-soname,$(call SONAME_FUNCTION,$(notdir $(1)),$(2))
 BUILDSHAREDLIB = yes

1 store items were analyzed:
  - 0 (0.0%) were identical
  - 1 (100.0%) differed
  - 0 (0.0%) were inconclusive
--8<---------------cut here---------------end--------------->8---

Ludo’.