Remove gn_bootstrap.sh

[andy31415]

This file was misleading because it actually runs activate.sh and it is generally a shell that just invokes another shell.

Now we run actual bootstrap for CI rather than activate.sh, which should ensure an up to date environment and avoid warnings of 'bootstrap done on a different machine'

It looks like the penalty of running a full bootstrap instead of activate.sh is about 80 seconds. While this is better than the old 5+ minutes of bootstrap, it is still somewhat slower with the benefit of likely a more "correct" build environment.

[github-actions]

PR #26335: Size comparison from 7be1954 to 06e23f4

Decreases (1 build for cc32xx)

platform	target	config	section	7be1954	06e23f4	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	19511285	19511284	-1	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	7be1954	06e23f4	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	604426	604426	0	0.0
			(read/write)	204156	204156	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197568	197568	0	0.0
			.comment	206	206	0	0.0
			.data	1468	1468	0	0.0
			.debug_abbrev	956872	956872	0	0.0
			.debug_aranges	101056	101056	0	0.0
			.debug_frame	341168	341168	0	0.0
			.debug_info	19511285	19511284	-1	-0.0
			.debug_line	2664965	2664965	0	0.0
			.debug_line_str	513	513	0	0.0
			.debug_loc	33340	33340	0	0.0
			.debug_loclists	1486884	1486884	0	0.0
			.debug_ranges	4984	4984	0	0.0
			.debug_rnglists	94239	94239	0	0.0
			.debug_str	3068127	3068127	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	104298	104298	0	0.0
			.shstrtab	265	265	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	480350	480350	0	0.0
			.symtab	287024	287024	0	0.0
			.text	498004	498004	0	0.0

[github-actions]

PR #26335: Size comparison from 7be1954 to c835514

Full report (1 build for cc32xx)

platform	target	config	section	7be1954	c835514	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	604426	604426	0	0.0
			(read/write)	204156	204156	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197568	197568	0	0.0
			.comment	206	206	0	0.0
			.data	1468	1468	0	0.0
			.debug_abbrev	956872	956872	0	0.0
			.debug_aranges	101056	101056	0	0.0
			.debug_frame	341168	341168	0	0.0
			.debug_info	19511285	19511285	0	0.0
			.debug_line	2664965	2664965	0	0.0
			.debug_line_str	513	513	0	0.0
			.debug_loc	33340	33340	0	0.0
			.debug_loclists	1486884	1486884	0	0.0
			.debug_ranges	4984	4984	0	0.0
			.debug_rnglists	94239	94239	0	0.0
			.debug_str	3068127	3068127	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	104298	104298	0	0.0
			.shstrtab	265	265	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	480350	480350	0	0.0
			.symtab	287024	287024	0	0.0
			.text	498004	498004	0	0.0