config.mak.dist: better cfg + 5.15.202 hash

[robang74]

Include a reference section about how changes impact and implies:

# Reported values relates to an i5-8365 fast-SSD and c.a. 18m compiling time
# # Recommended options for smal/fast build for deploying toolchain (w/ -pipe):
COMMON_CONFIG += CFLAGS="-g0 -O1 -pipe" CXXFLAGS="-g0 -O1 -pipe" LDFLAGS="-s"
# # Compressed size is 13% less than -O2 and, surprisingly, buildall +4% faster
# # COMMON_CONFIG += CFLAGS="-g0 -Os" CXXFLAGS="-g0 -Os" LDFLAGS="-s"
# # Compiles a toolchain for being faster in doing its works, but bigger size
# # COMMON_CONFIG += CFLAGS="-g0 -O2" CXXFLAGS="-g0 -O2" LDFLAGS="-s"
# # Pipe can increase the compilation speed of +6%, but it is sensitive:
# # COMMON_CONFIG += CFLAGS="-g0 -O2 -pipe" CXXFLAGS="-g0 -O2 -pipe" LDFLAGS="-s"
# Notes:
# # Definetely avoid -O3 because a single mistake in a toolchain avalanches
# # Recommended -O1 -pipe is +7% larger than -Os and -7% smaller than -O2
# # Recommended -O1 -pipe is 10% faster than -Os and +14% faster than -O2
``