[BUILD] Update Makefile with `MODE` variable that lets user combine multiple targets + more features #712

Job	Run time
Compilation Test (gcc)	44s
Compilation Test (clang)	23s
Compilation Test (clang-12)	23s
Combine Compilation Test Results	1s
Prepare Test Matrix	2s
Regression Test (b, Bonus Part) / Bonus Part	51s
Regression Test (d, Hardcore) / Hardcore	36s
Regression Test (m, Mandatory Part) / Mandatory Part	1m 25s
Regression Test (ne, Empty Env) / Empty Env	51s
Memory Leak Test (1_groups.sh)	33s
Memory Leak Test (1_operators.sh)	37s
Memory Leak Test (1_wildcards.sh)	1m 1s
Memory Leak Test (2_correction.sh)	1m 41s
Memory Leak Test (3_subshell.sh)	50s
Memory Leak Test (8_syntax_errors.sh)	1m 40s
Memory Leak Test (9_go_wild.sh)	49s
Memory Leak Test (leaks.sh)	1m 14s
Memory Leak Test (0_compare_parsing.sh)	1m 18s
Memory Leak Test (10_parsing_hell.sh)	1m 44s
Memory Leak Test (11_expansion.sh)	28s
Memory Leak Test (1_builtins_cd.sh)	1m 1s
Memory Leak Test (1_builtins_echo.sh)	1m 35s
Memory Leak Test (1_builtins_env.sh)	36s
Memory Leak Test (1_builtins_exit.sh)	1m 14s
Memory Leak Test (1_builtins_export.sh)	1m 7s
Memory Leak Test (1_builtins_pwd.sh)	35s
Memory Leak Test (1_builtins_unset.sh)	1m 14s
Memory Leak Test (1_pipelines.sh)	1m 28s
Memory Leak Test (1_redirs.sh)	1m 32s
Memory Leak Test (1_scmds.sh)	57s
Memory Leak Test (1_variables.sh)	1m 41s
Memory Leak Test (2_correction.sh)	1m 52s
Memory Leak Test (2_path_check.sh)	34s
Memory Leak Test (8_syntax_errors.sh)	1m 21s
Memory Leak Test (9_go_wild.sh)	48s
Memory Leak Test (1_segfault.sh)	1m 8s
Memory Leak Test (10_no_env.sh)	1m 3s
Combine Regression Test Results	1s
Combine Memory Leak Test Results	1s
	36m 59s

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