The first build that failed at BuildPackage stage is https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8926878301745646928

Selected error message:
chromeos-chrome-73.0.3644.0_alpha-r1: >>> Unpacking source...
chromeos-chrome-73.0.3644.0_alpha-r1: ERROR: ld.so: object 'libsandbox.so' from LD_PRELOAD cannot be preloaded (cannot open shared object file): ignored.

chromeos-chrome-73.0.3644.0_alpha-r1: package_version: Could not download URL (https://storage.googleapis.com/nativeclient-once/object/gcc_arm_x86_64_linux_a3129445edd74a320d1f3180707fe37548bba113.tgz): ('The read operation timed out',)
chromeos-chrome-73.0.3644.0_alpha-r1: Error: Command '/usr/bin/python2.7 src/build/download_nacl_toolchains.py --mode nacl_core_sdk sync --extract' returned non-zero exit status 1 in /home/chrome-bot/chrome_root
chromeos-chrome-73.0.3644.0_alpha-r1: Hook '/usr/bin/python2.7 src/build/download_nacl_toolchains.py --mode nacl_core_sdk sync --extract' took 61.21 secs
chromeos-chrome-73.0.3644.0_alpha-r1:  * ERROR: chromeos-base/chromeos-chrome-73.0.3644.0_alpha-r1::chromiumos failed (configure phase):
chromeos-chrome-73.0.3644.0_alpha-r1:  *   (no error message)

chromeos-chrome-73.0.3644.0_alpha-r1:  * Messages for package chromeos-base/chromeos-chrome-73.0.3644.0_alpha-r1 merged to /build/caroline/:
chromeos-chrome-73.0.3644.0_alpha-r1: 
chromeos-chrome-73.0.3644.0_alpha-r1:  * CHROME_ORIGIN VALUE is LOCAL_SOURCE
chromeos-chrome-73.0.3644.0_alpha-r1:  * /home/chrome-bot/chrome_root should be set here properly
chromeos-chrome-73.0.3644.0_alpha-r1:  * ERROR: chromeos-base/chromeos-chrome-73.0.3644.0_alpha-r1::chromiumos failed (configure phase):
chromeos-chrome-73.0.3644.0_alpha-r1:  *   (no error message)
chromeos-chrome-73.0.3644.0_alpha-r1:  * 
chromeos-chrome-73.0.3644.0_alpha-r1:  * Call stack:
chromeos-chrome-73.0.3644.0_alpha-r1:  *     ebuild.sh, line 133:  Called src_configure
chromeos-chrome-73.0.3644.0_alpha-r1:  *   environment, line 4361:  Called die
chromeos-chrome-73.0.3644.0_alpha-r1:  * The specific snippet of code:
chromeos-chrome-73.0.3644.0_alpha-r1:  *           CFLAGS="${CFLAGS} ${EBUILD_CFLAGS[*]}" CXXFLAGS="${CXXFLAGS} ${EBUILD_CXXFLAGS[*]}" LDFLAGS="${LDFLAGS} ${EBUILD_LDFLAGS[*]}" "${cmd[@]}" || die;
chromeos-chrome-73.0.3644.0_alpha-r1:  * 


It doesn't seem like a Chrome issue to me. Could it be possible to be an infra issue?