Clarify Makefile Contents

[jeremylt]

fixes #1766

I added some comments for clarity and grouped like content.

The only functional change is slightly expanding the make info output and adding a shorter make info-basic output.

When we're happy with this, we can migrate it to Ratel as well.

[jeremylt]

Sample new output:

$ make info-basic
-----------------------------------------
|     ___ __    ______________________  |
|    / (_) /_  / ____/ ____/ ____/ __ \ |
|   / / / __ \/ /   / __/ / __/ / / / / |
|  / / / /_/ / /___/ /___/ /___/ /_/ /  |
| /_/_/_.___/\____/_____/_____/_____/   |
-----------------------------------------

-----------------------------------------

Built-in Backends:
/cpu/self/ref/serial /cpu/self/ref/blocked /cpu/self/opt/serial /cpu/self/opt/blocked

Additional Backends:
/cpu/self/memcheck/serial /cpu/self/memcheck/blocked /cpu/self/avx/serial /cpu/self/avx/blocked /cpu/self/xsmm/serial /cpu/self/xsmm/blocked /gpu/cuda/ref /gpu/cuda/shared /gpu/cuda/gen

-----------------------------------------

$ make info
-----------------------------------------
|     ___ __    ______________________  |
|    / (_) /_  / ____/ ____/ ____/ __ \ |
|   / / / __ \/ /   / __/ / __/ / / / / |
|  / / / /_/ / /___/ /___/ /___/ /_/ /  |
| /_/_/_.___/\____/_____/_____/_____/   |
-----------------------------------------

-----------------------------------------

Built-in Backends:
/cpu/self/ref/serial /cpu/self/ref/blocked /cpu/self/opt/serial /cpu/self/opt/blocked

Additional Backends:
/cpu/self/memcheck/serial /cpu/self/memcheck/blocked /cpu/self/avx/serial /cpu/self/avx/blocked /cpu/self/xsmm/serial /cpu/self/xsmm/blocked /gpu/cuda/ref /gpu/cuda/shared /gpu/cuda/gen

-----------------------------------------

Compiler Flags:
CC            = gcc-13
CXX           = g++-13
FC            = gfortran
CPPFLAGS      = -I./include
CFLAGS        = -O -march=native -g -ffp-contract=fast -fopenmp-simd -fPIC -std=c99 -Wall -Wextra -Wno-unused-parameter -MMD -MP  
CXXFLAGS      = -O -march=native -g -ffp-contract=fast -fopenmp-simd -fPIC -std=c++11 -Wall -Wextra -Wno-unused-parameter -MMD -MP 
FFLAGS        = -O -march=native -g -ffp-contract=fast -fopenmp-simd -fPIC -cpp -Wall -Wextra -Wno-unused-parameter -Wno-unused-dummy-argument -MMD -MP 
NVCCFLAGS     = -ccbin g++-13 -Xcompiler "-O -march=native -g -ffp-contract=fast -fopenmp-simd" -Xcompiler -fPIC -arch=sm_89
HIPCCFLAGS    = -O -march=native -g -ffp-contract=fast -fPIC -munsafe-fp-atomics
SYCLFLAGS     =  -fPIC -std=c++17 -O -march=native -g -ffp-contract=fast -fopenmp-simd -fPIC -Wall -Wextra -Wno-unused-parameter -MMD -MP -O -march=native -g -ffp-contract=fast
CEED_LDFLAGS  = 
CEED_LDLIBS   = -lm
AR            = ar
ARFLAGS       = crD
OPT           = -O -march=native -g -ffp-contract=fast -fopenmp-simd
AFLAGS        = -fsanitize=address 
ASAN          = (empty)
VERBOSE       = (empty) [verbose=off]

-----------------------------------------

Backend Dependencies:
MEMCHK_STATUS = Enabled [backends: /cpu/self/memcheck/serial /cpu/self/memcheck/blocked]
AVX_STATUS    = Enabled [backends: /cpu/self/avx/serial /cpu/self/avx/blocked]
XSMM_DIR      = ../libxsmm [backends: /cpu/self/xsmm/serial /cpu/self/xsmm/blocked]
CUDA_DIR      = /opt/cuda [backends: /gpu/cuda/ref /gpu/cuda/shared /gpu/cuda/gen]
ROCM_DIR      =  [not found]
SYCL_DIR      =  [not found]
MAGMA_DIR     = ../magma [not found]
OCCA_DIR      = ../occa/install [not found]

-----------------------------------------

Example Dependencies:
MFEM_DIR      = ../mfem
NEK5K_DIR     = 
PETSC_DIR     = 
DEAL_II_DIR   = ../dealii/install

-----------------------------------------

Install Options:
prefix        = /usr/local
includedir    = $(prefix)/include
libdir        = $(prefix)/lib
pkgconfigdir  = $(libdir)/pkgconfig

-----------------------------------------

[jrwrigh]

LGTM. Thanks for the cleanup effort!