Update docs regarding tilde substitution (backported from 9.0). For T… #4583

Job	Run time
gcc	12m 37s
gcc (CFLAGS=-DTCL_NO_DEPRECATED=1)	12m 35s
gcc (--disable-shared)	12m 56s
gcc (--disable-zipfs)	12m 27s
gcc (--enable-symbols)	12m 43s
gcc (--enable-symbols=mem)	14m 23s
gcc (--enable-symbols=all)	15m 38s
msvc	10m 39s
msvc (CHECKS=nodep)	10m 27s
msvc (OPTS=static)	10m 53s
msvc (OPTS=noembed)	10m 5s
msvc (OPTS=symbols)	10m 43s
msvc (OPTS=symbols STATS=compdbg,memdbg)	15m 38s
	2h 41m 44s

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