dependencies.sh: improve the missing perl modules detection

---
Changes v6 -> v7:
- Remove the "space-separated list" comment. Having two examples of how to add modules to the list makes this comment not necessary. (Suggested by Thomas Petazzoni)
- Don't use the += operator as is bash specific and not POSIX compliant. The script specifies #!/bin/sh so we are not guaranteed that it will be executed with bash. (Suggested by Thomas Petazzoni)
- Use just "echo" without the empty string argument to produce blank lines. (Suggested by Thomas Petazzoni)

Changes v5 -> v6:
- Remove the check for perl itself, as is already done at line #161.

Changes v4 -> v5:
- Use the string concatenation operator (+=) to assing the values to the required_perl_modules. That way the comments about why each module is needed can be in the same line where the module is added to the variable.
Use also += for the missing_perl_modules variable.

Changes v3 -> v4:
- Thread::Queue module is actually needed because host-automake uses it. Comment modified accordingly. (Highlighted by Thomas Petazzoni)

Changes v2 -> v3:
- Add comments about why each module is needed. (Suggested by Baruch Siach)

Changes v1 -> v2:
- Check first for perl itself, and then the modules. Also keep the comment which says that perl is needed to build host-autoconf. (Suggested by Baruch Siach)

 support/dependencies/dependencies.sh |   26 +++++++++++++++++++++-----
 1 files changed, 21 insertions(+), 5 deletions(-)

index 01ad828..c83d787 100755
@@ -236,10 +236,26 @@ if grep -q ^BR2_HOSTARCH_NEEDS_IA32_COMPILER=y $BR2_CONFIG ; then
 	fi
 fi
 
-# Check that the Perl installation is complete enough to build
-# host-autoconf.
-if ! perl  -e "require Data::Dumper" > /dev/null 2>&1 ; then
-	echo "Your Perl installation is not complete enough, at least Data::Dumper is missing."
-	echo "On Debian/Ubuntu distributions, install the 'perl' package."
+# Check that the Perl installation is complete enough for Buildroot.
+required_perl_modules="Data::Dumper" # Needed to build host-autoconf
+required_perl_modules="$required_perl_modules Thread:Queue" # Used by host-automake
+
+# This variable will keep the modules that are missing in your system.
+missing_perl_modules=""
+
+for pm in $required_perl_modules ; do
+	if ! perl  -e "require $pm" > /dev/null 2>&1 ; then
+		missing_perl_modules="$missing_perl_modules $pm"
+	fi
+done
+
+if [ -n "$missing_perl_modules" ] ; then
+	echo "Your Perl installation is not complete enough; at least the following"
+	echo "modules are missing:"
+	echo
+	for pm in $missing_perl_modules ; do
+		echo -e "\t $pm"
+	done
+	echo
 	exit 1
 fi

1.7.1

Vicente,

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com