First time, "Rebuild Solution":
Compiling 'blinkbuttonandweb' for 'LOLIN(WEMOS) D1 R2 & mini'
Creating BIN file elease/blinkbuttonandweb.ino.bin" using elease/blinkbuttonandweb.ino.elf"
Program size: 320,324 bytes (used 31% of a 1,044,464 byte maximum) (56.89 secs)
Minimum Memory Usage: 28568 bytes (35% of a 81920 byte maximum)
Second time, no changes, control-shift-B:
Compiling 'blinkbuttonandweb' for 'LOLIN(WEMOS) D1 R2 & mini'
Creating BIN file elease/blinkbuttonandweb.ino.bin" using elease/blinkbuttonandweb.ino.elf"
Program size: 320,324 bytes (used 31% of a 1,044,464 byte maximum) (2.51 secs)
Minimum Memory Usage: 28568 bytes (35% of a 81920 byte maximum)
Third time, no changes, control-shift-B:
Compiling 'blinkbuttonandweb' for 'LOLIN(WEMOS) D1 R2 & mini'
Creating BIN file elease/blinkbuttonandweb.ino.bin" using elease/blinkbuttonandweb.ino.elf"
Program size: 320,324 bytes (used 31% of a 1,044,464 byte maximum) (33.24 secs)
Minimum Memory Usage: 28568 bytes (35% of a 81920 byte maximum)
Fourth time, no changes..., control-shift-B …
Compiling 'blinkbuttonandweb' for 'LOLIN(WEMOS) D1 R2 & mini'
Creating BIN file elease/blinkbuttonandweb.ino.bin" using elease/blinkbuttonandweb.ino.elf"
Program size: 320,324 bytes (used 31% of a 1,044,464 byte maximum) (4.87 secs)
Minimum Memory Usage: 28568 bytes (35% of a 81920 byte maximum)
Fifth time, same procedure:
Compiling 'blinkbuttonandweb' for 'LOLIN(WEMOS) D1 R2 & mini'
Creating BIN file elease/blinkbuttonandweb.ino.bin" using elease/blinkbuttonandweb.ino.elf"
Program size: 320,324 bytes (used 31% of a 1,044,464 byte maximum) (33.66 secs)
Minimum Memory Usage: 28568 bytes (35% of a 81920 byte maximum)
Obviously not expected predictable behavior of a properly functioning make.