Add arm64 support

This patch adds `--config=arm64` and `--cpu=arm64` flags for users to
compile for the 64-bit version of the Raspberry Pi.

The existing 32-bit ARM build should still work. This patch only adds
additional 64-bit capabilities. Future patches can remove 32-bit
support.

Eigen needed some tweaks because we have `LDBL_MANT_DIG` of 113 on
arm64. None of the code paths that used the parameters `U` and `V`
actually gets compiled in. Adding `[[maybe_unused]]` fixed the error.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: Ibf919b2964fe971769449a1c556c13e3bf1d48e9
diff --git a/debian/BUILD b/debian/BUILD
index 76bcf28..2aeabf2 100644
--- a/debian/BUILD
+++ b/debian/BUILD
@@ -47,6 +47,10 @@
     python_gtk_debs = "files",
 )
 load(
+    ":opencv_arm64.bzl",
+    opencv_arm64_debs = "files",
+)
+load(
     ":opencv_armhf.bzl",
     opencv_armhf_debs = "files",
 )
@@ -387,6 +391,12 @@
 )
 
 generate_deb_tarball(
+    name = "opencv_arm64",
+    files = opencv_arm64_debs,
+    target_compatible_with = ["@platforms//os:linux"],
+)
+
+generate_deb_tarball(
     name = "opencv_armhf_v4",
     files = opencv_armhf_debs,
     target_compatible_with = ["@platforms//os:linux"],