d/rules: Factor out computation of system library path into a script

Breaking it up one line per command makes it easier to add more code than
when it was inlined it into debian/rules, and avoids needing to double
the $ for shell variables.

Based on a patch sent to pkg-config for #992620, but taking the fix
for #792285 into account in this version.

Signed-off-by: Simon McVittie <smcv@debian.org>

2 files changed, 17 insertions, 4 deletions

diff --git a/debian/rules b/debian/rules
index 35fa4cb..3f58ea5 100755
--- a/debian/rules
+++ b/debian/rules
@@ -21,10 +21,7 @@ else
    GCC = gcc
 endif
 
-SYSTEM_LIBDIRS := $(shell for opt in '' $$($${CC-$(GCC)} -print-multi-lib | sed -n -e's/.*;@/-/p'); do \
-     $(GCC) $$opt -print-search-dirs | sed -n -e's/^libraries: =//p' \
-     | sed -e's/:/\n/g' | xargs -n1 readlink -f | grep -v 'gcc\|/[0-9.]\+$$'; \
-    done | LC_ALL=C sort -u | tr '\n' : | sed 's/:$$//')
+SYSTEM_LIBDIRS := $(shell sh debian/system-libdirs.sh $(GCC))
 
 %:
 	dh $@
diff --git a/debian/system-libdirs.sh b/debian/system-libdirs.sh
new file mode 100755
index 0000000..d011a31
--- /dev/null
+++ b/debian/system-libdirs.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+
+set -eu
+
+gcc="$1"
+
+for opt in '' $(${CC-"$gcc"} -print-multi-lib | sed -n -e's/.*;@/-/p'); do
+    "$gcc" $opt -print-search-dirs |
+    sed -n -e 's/^libraries: =//p' |
+    sed -e 's/:/\n/g' |
+    xargs -n1 readlink -f |
+    grep -v 'gcc\|/[0-9.]\+$'
+done |
+LC_ALL=C sort -u |
+tr '\n' : |
+sed 's/:$//'