libbacktrace: only match magic number at start of line

libbacktrace/ChangeLog:
	PR libbacktrace/96971
	* filetype.awk: Only match magic number at start of line.

Author: ianlancetaylor

filetype.awk

@@ -1,13 +1,13 @@
 # An awk script to determine the type of a file.
-/\177ELF\001/      { if (NR == 1) { print "elf32"; exit } }
-/\177ELF\002/      { if (NR == 1) { print "elf64"; exit } }
-/\114\001/         { if (NR == 1) { print "pecoff"; exit } }
-/\144\206/         { if (NR == 1) { print "pecoff"; exit } }
-/\001\337/         { if (NR == 1) { print "xcoff32"; exit } }
-/\001\367/         { if (NR == 1) { print "xcoff64"; exit } }
-/\376\355\372\316/ { if (NR == 1) { print "macho"; exit } }
-/\316\372\355\376/ { if (NR == 1) { print "macho"; exit } }
-/\376\355\372\317/ { if (NR == 1) { print "macho"; exit } }
-/\317\372\355\376/ { if (NR == 1) { print "macho"; exit } }
-/\312\376\272\276/ { if (NR == 1) { print "macho"; exit } }
-/\276\272\376\312/ { if (NR == 1) { print "macho"; exit } }
+/^\177ELF\001/      { if (NR == 1) { print "elf32"; exit } }
+/^\177ELF\002/      { if (NR == 1) { print "elf64"; exit } }
+/^\114\001/         { if (NR == 1) { print "pecoff"; exit } }
+/^\144\206/         { if (NR == 1) { print "pecoff"; exit } }
+/^\001\337/         { if (NR == 1) { print "xcoff32"; exit } }
+/^\001\367/         { if (NR == 1) { print "xcoff64"; exit } }
+/^\376\355\372\316/ { if (NR == 1) { print "macho"; exit } }
+/^\316\372\355\376/ { if (NR == 1) { print "macho"; exit } }
+/^\376\355\372\317/ { if (NR == 1) { print "macho"; exit } }
+/^\317\372\355\376/ { if (NR == 1) { print "macho"; exit } }
+/^\312\376\272\276/ { if (NR == 1) { print "macho"; exit } }
+/^\276\272\376\312/ { if (NR == 1) { print "macho"; exit } }