Better build-time error messages

Currently, when building from source if you are missing certain things (like compilers...) the build fails with very verbose errors containing many things that are not relevant:

[imcinerney@pi3 1.5]$ make
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   497  100   497    0     0    679      0 --:--:-- --:--:-- --:--:--   678
100  388k  100  388k    0     0   228k      0  0:00:01  0:00:01 --:--:--  642k
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   497  100   497    0     0    719      0 --:--:-- --:--:-- --:--:--   719
100 18235  100 18235    0     0  14506      0  0:00:01  0:00:01 --:--:-- 86833
/bin/sh: gfortran: command not found
/bin/sh: g++: command not found
Traceback (most recent call last):
  File "/home/imcinerney/dev/julia/main/1.5/contrib/normalize_triplet.py", line 120, in <module>
    }[list(filter(lambda x: re.match("\d+\.\d+(\.\d+)?", x), sys.argv[2].split()))[-1].split('.')[0]]
IndexError: list index out of range
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   453  100   453    0     0   1038      0 --:--:-- --:--:-- --:--:--  1036
  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
curl: (22) The requested URL returned error: 404 Not Found
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404 Not Found
make[1]: *** [/home/imcinerney/dev/julia/main/1.5/deps/suitesparse.mk:144: /home/imcinerney/dev/julia/main/1.5/deps/srccache/SuiteSparse.v5.4.0-6..tar.gz] Error 22
make: *** [Makefile:60: julia-deps] Error 2

This error should be highlighting the fact that there is a problem with finding the programs gfortran and g++, but currently those errors are hidden by the Python traceback and the curl errors (so when I first saw this my immediate thought was a regression with detecting GCC10 again, since that traceback is in the same place).