fix(scripts/termux_step_install_license): fix logic error

Move counter advance to the end of the while loop.
This fixes a logic error where the counter wouldn't advance
if the first license was "generic", and the second one was
author specific. This would cause `cp` to attempt to copy
through the dangling symlink to the generic license
in `termux-licenses` which fails and dies.

scripts/build/termux_step_install_license.sh

@@ -32,6 +32,7 @@ termux_step_install_license() {
 		done <<< "${TERMUX_PKG_LICENSE_FILE//,/$'\n'}"
 	else # If a license file wasn't specified, find the one we need
 		local TO_LICENSE             # link target for generic licenses
+		local FROM_SOURCES=0         # flag to check if we've included licenses from the source files yet
 		local COMMON_LICENSE_FILES=( # search list for licenses with copyright information
 		'COPYING' 'Copyright.txt'
 		'copyright' 'Copyright' 'COPYRIGHT'
@@ -52,35 +53,43 @@ termux_step_install_license() {
 				'BSD'|'BSD 2-Clause'|'BSD 3-Clause'|'BSD Simplified'\
 				|'curl'|'HPND'|'ISC'|'Libpng'|'MIT'|'Openfont-1.1'\
 				|'PythonPL'|'X11'|'ZLIB')
-				# Find the license file in the source files
-				for FILE in "${COMMON_LICENSE_FILES[@]}"; do
-					[[ -f "$TERMUX_PKG_SRCDIR/$FILE" ]] && {
-						if (( COUNTER )); then
-							cp -f "${TERMUX_PKG_SRCDIR}/$FILE" "${TERMUX_PREFIX}/share/doc/${TERMUX_PKG_NAME}/copyright.${COUNTER}"
-						else
-							cp -f "${TERMUX_PKG_SRCDIR}/$FILE" "${TERMUX_PREFIX}/share/doc/${TERMUX_PKG_NAME}/copyright"
-						fi
-						# since this is a post-increment, (( 0 )) would be falsey
-						# thus `set -e` would kill the script on the first iteration
-						# using `true` prevents this
-						: $(( COUNTER++ ))
-					}
-				done
+				# We only want to include the license files from the source files once
+				if (( ! FROM_SOURCES )); then
+					local FILE
+					# Find the license file(s) in the source files
+					for FILE in "${COMMON_LICENSE_FILES[@]}"; do
+						[[ -f "$TERMUX_PKG_SRCDIR/$FILE" ]] && {
+							if (( COUNTER )); then
+								cp -f "${TERMUX_PKG_SRCDIR}/$FILE" "${TERMUX_PREFIX}/share/doc/${TERMUX_PKG_NAME}/copyright.${COUNTER}"
+							else
+								cp -f "${TERMUX_PKG_SRCDIR}/$FILE" "${TERMUX_PREFIX}/share/doc/${TERMUX_PKG_NAME}/copyright"
+							fi
+							(( ++COUNTER, ++FROM_SOURCES ))
+						}
+					done
+					# If we have not found any licenses after searching, that's an error.
+					if (( ! FROM_SOURCES )); then
+						termux_error_exit "${TERMUX_PKG_NAME}: Could not find a license file for $LICENSE in the package sources"
+					fi
+				fi
 				;;
-				# For the rest we can use a link to the generic license file
-				*) [[ -f "$TERMUX_SCRIPTDIR/packages/termux-licenses/LICENSES/${LICENSE}.txt" ]] && {
-						# the link target depends on the libc being used
-						if [[ "$TERMUX_PACKAGE_LIBRARY" == 'bionic' ]]; then
-							TO_LICENSE="../../LICENSES/${LICENSE}.txt"
-						elif [[ "$TERMUX_PACKAGE_LIBRARY" == 'glibc' ]]; then
-							TO_LICENSE="../../../../share/LICENSES/${LICENSE}.txt"
-						fi
-						if (( COUNTER )); then
-							ln -sf "$TO_LICENSE" "$TERMUX_PREFIX/share/doc/$TERMUX_PKG_NAME/copyright.$((COUNTER++))"
-						else
-							ln -sf "$TO_LICENSE" "$TERMUX_PREFIX/share/doc/$TERMUX_PKG_NAME/copyright"
-						fi
-					}
+				*) # For the rest we can use a link to the generic license file
+				[[ -f "$TERMUX_SCRIPTDIR/packages/termux-licenses/LICENSES/${LICENSE}.txt" ]] || {
+					# If we get here, no license file could be found
+					termux_error_exit "${TERMUX_PKG_NAME}: Could not find a license file for $LICENSE in packages/termux-licenses"
+				}
+				# the link target depends on the libc being used
+				case "$TERMUX_PACKAGE_LIBRARY" in
+					'bionic') TO_LICENSE="../../LICENSES/${LICENSE}.txt";;
+					'glibc')  TO_LICENSE="../../../../share/LICENSES/${LICENSE}.txt";;
+					*)        termux_error_exit "'$TERMUX_PACKAGE_LIBRARY' is not a supported libc";;
+				esac
+				if (( COUNTER )); then
+					ln -sf "$TO_LICENSE" "$TERMUX_PREFIX/share/doc/$TERMUX_PKG_NAME/copyright.${COUNTER}"
+				else
+					ln -sf "$TO_LICENSE" "$TERMUX_PREFIX/share/doc/$TERMUX_PKG_NAME/copyright"
+				fi
+				(( ++COUNTER ))
 				;;
 			esac
 		done <<< "${TERMUX_PKG_LICENSE//,/$'\n'}"