meson: use "sh -eu" and make .sh +x, .py -x

Shell scripts should be executable so that meson reports their
invocation succinctly (does not print 'sh' '-e').
Python scripts should not be executable so that meson does the
detection of the right python binary itself.

Add -u everywhere to catch potential errors.

src/basic/generate-af-list.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/sh -eu
 
 $1 -E -dM -include sys/socket.h - </dev/null | \
     grep -Ev 'AF_UNSPEC|AF_MAX' | \

src/basic/generate-arphrd-list.sh

@@ -1,4 +1,4 @@
-#!/bin/sh -e
+#!/bin/sh -eu
 
 $1 -dM -include net/if_arp.h - </dev/null | \
     awk '/^#define[ \t]+ARPHRD_[^ \t]+[ \t]+[^ \t]/ { print $2; }' | \

src/basic/generate-cap-list.sh

@@ -1,4 +1,4 @@
-#!/bin/sh -e
+#!/bin/sh -eu
 
 $1 -dM -include linux/capability.h -include "$2" -include "$3" - </dev/null | \
     awk '/^#define[ \t]+CAP_[A-Z_]+[ \t]+/ { print $2; }' | \

src/basic/generate-errno-list.sh

@@ -1,4 +1,4 @@
-#!/bin/sh -e
+#!/bin/sh -eu
 
 $1 -dM -include errno.h - </dev/null | \
     awk '/^#define[ \t]+E[^ _]+[ \t]+/ { print $2; }'