> Why is the executable named ./a.out and not ./lolno?

  $ ls
  lolno.c
  $ make lolno
  cc     lolno.c   -o lolno
  $ ls
  lolno lolno.c

Sure. Here's viola, a web browser from the early 90s, with a replacement makefile (GNU make) that's a bit more sane:

    CC      = gcc -std=c99 -Wall -Wextra -pedantic
    CFLAGS  = -g
    LDFLAGS = -g
    LDLIBS  = -L/usr/X11R6/lib -lICE -lSM -lXpm -lX11 -lXext -lXmu -lXt -lm

    VIOLA_PATH := $(shell pwd)/resources

    override CFLAGS += -DPOSIX_C_SOURCE=199309L         \
                    -D_POSIX_SOURCE -D_XOPEN_SOURCE     \
                    -D_BSD_SOURCE -D_SVID_SOURCE        \
                    -DDEFAULT_VIOLA_PATH='"$(VIOLA_PATH)"'\
                    -DVIOLA

    %.a:
            $(AR) $(ARFLAGS) $@ $?

    viola/viola: $(patsubst %.c,%.o,$(wildcard viola/*.c)) \
                    libIMG/libIMG.a     \
                    libXPA/src/libxpa.a \
                    libStyle/libStyle.a \
                    libWWW/libWWW.a     \
                    parmcheck.o

    libIMG/libIMG.a     : $(patsubst %.c,%.o,$(wildcard libIMG/*.c))
    libXPA/src/libxpa.a : $(patsubst %.c,%.o,$(wildcard libXPA/src/*.c))
    libStyle/libStyle.a : $(patsubst %.c,%.o,$(wildcard libStyle/*.c))
    libWWW/libWWW.a     : $(patsubst %.c,%.o,$(wildcard libWWW/*.c))

It's 155,000 lines of C code across 361 files. Not shown are the nearly 900 lines that make up the dependencies, but using `makedepend` (which came with my system) makes short work of that. I have a more complicated project that compiles an application written in Lua into a Linux executable. It wasn't hard to write, given that you can always add new rules to `make`, such as converting a `.lua` file to a `.o` file:

    %.o : %.lua
            $(BIN2C) $(B2CFLAGS) -o $*.l.c $<
            $(CC) $(CFLAGS) -c -o $@ $*.l.c
            $(RM) $*.l.c

Okay, that requires a custom tool (`bin2c`) but can other build systems do this? I honestly don't know.

That still doesn't require any flags. Where it starts to get complicated is when you link in system libraries, because they vary between OSes and different versions/distros of the same OS. If you need to support multiple platforms this quickly becomes combinatorially complex, which is where Makefile hell comes from.

Use stunnel for TLS. A benefit is that if you properly sandbox the daemon behind it, a compromise in the daemon behind TLS does not result in the server key being compromised.

A GUI could be done in SDL+Nuklear, GTK+ or others.

Database access from C is easy, since the databases are written in C and provide C APIs for access.