linker: add LD_SHOW_AUXV support.

Yes, `od -t d8 /proc/self/auxv` is clever:
```
$ adb shell od -t d8 /proc/self/auxv
0000000                      33            488593047552
0000020                      51                    4720
0000040                      16                 1155071
0000060                       6                    4096
0000100                      17                     100
0000120                       3            375971917888
0000140                       4                      56
0000160                       5                      12
0000200                       7            488593051648
0000220                       8                       0
0000240                       9            375972184064
0000260                      11                       0
0000300                      12                       0
0000320                      13                       0
0000340                      14                       0
0000360                      23                       0
0000400                      25            549220780840
0000420                      26                       0
0000440                      31            549220786153
0000460                      15            549220780856
0000500                       0                       0
0000520
$
```
But this is a lot easier to read:
```
$ adb shell LD_SHOW_AUXV=1 date
AT_SYSINFO_EHDR      0x7065010000
AT_MINSIGSTKSZ       4720
AT_HWCAP             0b100011001111111111111
AT_PAGESZ            4096
AT_CLKTCK            100
AT_PHDR              0x5c79d60040
AT_PHENT             56
AT_PHNUM             12
AT_BASE              0x7065011000
AT_FLAGS             0
AT_ENTRY             0x5c79da1000
AT_UID               0
AT_EUID              0
AT_GID               0
AT_EGID              0
AT_SECURE            0
AT_RANDOM            0x7ff814eb98
AT_HWCAP2            0
AT_EXECFN            "/system/bin/date"
AT_PLATFORM          "aarch64"
Tue Aug 22 20:43:22 GMT 2023
```

Test: adb shell LD_SHOW_AUXV=1 date
Change-Id: I51c4e8cbb799eb1dc360c9417cc6f82bebdcda73
diff --git a/linker/NOTICE b/linker/NOTICE
index d61a193..7fd1877 100644
--- a/linker/NOTICE
+++ b/linker/NOTICE
@@ -362,3 +362,31 @@
 
 -------------------------------------------------------------------
 
+Copyright (C) 2023 The Android Open Source Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in
+   the documentation and/or other materials provided with the
+   distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
+
+-------------------------------------------------------------------
+