Make dist causes reported CFLAGS at runtime to be incorrect

When building SWIFT from a make dist archive the CFLAGS reported are incorrect at runtime.

[0000] [00000.0] main: MPI is up and running with 216 node(s).

 Welcome to the cosmological hydrodynamical code
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 SPH With Inter-dependent Fine-grained Tasking

 Version : 0.8.0
 Revision: v0.7.0-3123-gb73901b5-dirty, Branch: master, Date: 2019-02-20 10:39:24 +0000
 Webpage : www.swiftsim.com

 Config. options: '--with-parmetis --with-tbbmalloc --enable-ipo CFLAGS=-qopt-zmm-usage=high'

 Compiler: ICC, Version: 18.0.20180210
 CFLAGS  : '-flto -O3 -fomit-frame-pointer -malign-double -fstrict-aliasing -ffast-math -funroll-loops -march=skylake-avx512 -mavx512dq -pthread -Wall -Wextra -Wno-unused-parameter -Wshadow -Werror -Wstrict-prototypes'

 HDF5 library version: 1.10.3
 FFTW library version: 3.x (details not available)
 GSL  library version: 2.4
 MPI library: Open MPI v3.0.1 (MPI std v3.1)
 ParMETIS library version: 4.0.3

I get GNU compiler flags reported when compiling with ICC.