MFC r320252, r320686, r325769:
r320252:
In release/release.sh:
- Rename chroot_arm_armv6_build_release() to chroot_arm_build_release()
and make it hardware agnostic (such as armv6 -vs- armv7 -vs- arm64).
- Evaluate EMBEDDED_TARGET differently so release/tools/arm.subr can
be used for arm/armv6 and arm64/aarch64.
- Update comments and copyright.

In release/tools/arm.subr:
- In arm_create_disk(), change the default alignment from 63 to 512k,
fixing a boot issue on arm64 and EFI. [1]
- Update comments and copyright.

r320686:
Fix the ftp-stage target by loosening the constraints on the TARGET
and TARGET_ARCH variables.

r325769:
Update the GUMSTIX image build to use arm/arm TARGET/TARGET_ARCH.
Update the TARGET/TARGET_ARCH matching in release/release.sh and
release/Makefile.mirrors for simplification.

Note: The RPI3.conf addition from r320252 is not included, as it is
not supported on 10-STABLE. Additionally, arm64/aarch64 changes are
also excluded from this commit.

Sponsored by: The FreeBSD Foundation

MFC r289337:
Deprecate MD5 checksum generation in favor of SHA512.

This was discussed during the 10.2-RELEASE cycle, however
since we were nearing the end of the cycle, we decided to
defer this change until after 10.2-RELEASE.

Sponsored by: The FreeBSD Foundation

MFC r284780, r284811, r284812:

r284780:
Ensure ASSUME_ALWAYS_YES is set when deleting pkg(8) from the
DESTDIR, otherwise it can get stuck in ttyin.

r284811:
Consider PRERELEASE builds snapshots, in addition to CURRENT
and STABLE.

r284812:
Change the hour:minute delimiter from ':' to '-', since
the former is an invalid character in EC2 images.

Approved by: re (glebius, insta-MFC)
Sponsored by: The FreeBSD Foundation

MFC r283573, r283574, r283575, r283576, r283580, r283593, r283618:

r283573:
Remove a continuation on error, since the relevant behavior can
only occur if a particular file exists.

r283574:
Set STAGE_TARGETS only if RELEASEDIR exists.

r283575:
Remove duplicate exists() sanity check.

r283576:
Reindent after previous commit.

r283580:
Use SVNREVISION and BUILDDATE if passed into the make(1)
environment, fallback to trying to figure it out otherwise.

r283593:
Fix a typo in a comment.

r283618:
Invert the build date and svn revision to match the namimg
convention that has been in use for a while.

Sponsored by: The FreeBSD Foundation

MFC r282785, r282787, r282789, r282790, r282791, r282792, r282793,
r282794, r282795, r282796, r282797, r282798, r282799, r283265,
r283266, r283268, r283271, r283272, r283298, r283302:

Add a new file, Makefile.mirrors, which is intended to replace
a 474-line kludge of a shell script to pre-create the directory
hierarchy on ftp-master.

This is not in any way connected to the build, and there is no
intention to do so. This only intent here is to try to make
things a little bit easier.

Always use the 'make install' directory as the source for images.
For RE purposes, we use the default (/R within the chroot), so
this helps avoid copying files multiple times and xz(1)-compressing
additional times when not needed.

Fix staging virtual machine images for ftp propagation.

This Makefile is not for general consumption.

Sponsored by: The FreeBSD Foundation

MFC r284780, r284811, r284812:

r284780:
Ensure ASSUME_ALWAYS_YES is set when deleting pkg(8) from the
DESTDIR, otherwise it can get stuck in ttyin.

r284811:
Consider PRERELEASE builds snapshots, in addition to CURRENT
and STABLE.

r284812:
Change the hour:minute delimiter from ':' to '-', since
the former is an invalid character in EC2 images.

Approved by: re (glebius, insta-MFC)
Sponsored by: The FreeBSD Foundation

MFC r283573, r283574, r283575, r283576, r283580, r283593, r283618:

r283573:
Remove a continuation on error, since the relevant behavior can
only occur if a particular file exists.

r283574:
Set STAGE_TARGETS only if RELEASEDIR exists.

r283575:
Remove duplicate exists() sanity check.

r283576:
Reindent after previous commit.

r283580:
Use SVNREVISION and BUILDDATE if passed into the make(1)
environment, fallback to trying to figure it out otherwise.

r283593:
Fix a typo in a comment.

r283618:
Invert the build date and svn revision to match the namimg
convention that has been in use for a while.

Sponsored by: The FreeBSD Foundation

MFC r282785, r282787, r282789, r282790, r282791, r282792, r282793,
r282794, r282795, r282796, r282797, r282798, r282799, r283265,
r283266, r283268, r283271, r283272, r283298, r283302:

Add a new file, Makefile.mirrors, which is intended to replace
a 474-line kludge of a shell script to pre-create the directory
hierarchy on ftp-master.

This is not in any way connected to the build, and there is no
intention to do so. This only intent here is to try to make
things a little bit easier.

Always use the 'make install' directory as the source for images.
For RE purposes, we use the default (/R within the chroot), so
this helps avoid copying files multiple times and xz(1)-compressing
additional times when not needed.

Fix staging virtual machine images for ftp propagation.

This Makefile is not for general consumption.

Sponsored by: The FreeBSD Foundation