Drop compiler variables from spack load (#21699)

Drops:

* C_INCLUDE_PATH
* CPLUS_INCLUDE_PATH
* LIBRARY_PATH
* INCLUDE

We already decided to use C_INCLUDE_PATH, CPLUS_INCLUDE_PATH, INCLUDE over CPATH here:

https://github.com/spack/spack/pull/14749

However, none of these flags apply to Fortran on Linux. So for consistency it seems better to make the user use -I and -L flags by hand or through pkgconfig.

etc/spack/defaults/modules.yaml

@@ -25,16 +25,6 @@ modules:
       - MANPATH
     share/aclocal:
       - ACLOCAL_PATH
-    lib:
-      - LIBRARY_PATH
-    lib64:
-      - LIBRARY_PATH
-    include:
-      - C_INCLUDE_PATH
-      - CPLUS_INCLUDE_PATH
-      # The INCLUDE env variable specifies paths to look for
-      # .mod file for Intel Fortran compilers
-      - INCLUDE
     lib/pkgconfig:
       - PKG_CONFIG_PATH
     lib64/pkgconfig:

share/spack/qa/setup-env-test.sh

@@ -109,7 +109,6 @@ succeeds spack -m load b
 fails spack -m load -l
 # test a variable MacOS clears and one it doesn't for recursive loads
 contains "export LD_LIBRARY_PATH=$(spack -m location -i a)/lib:$(spack -m location -i b)/lib" spack -m load --sh a
-contains "export LIBRARY_PATH=$(spack -m location -i a)/lib:$(spack -m location -i b)/lib" spack -m load --sh a
 succeeds spack -m load --only dependencies a
 succeeds spack -m load --only package a
 fails spack -m load d