Trac #29345: replace the function that populates the CVXOPT_* variables.

Our existing function, borrowed from Gentoo, to populate the CVXOPT_*
variables from pkg-config was brittle. It didn't handle -lpthread and
-lm the way it was intended to, and didn't always work with a non-bash
shell. The new version (which has also been upstreamed to Gentoo)
should fix both of those problems. It also suppors getting the -L and
-I flags from pkg-config in the future, which will likely be necessary
to support system installations of some cvxopt dependencies.

build/pkgs/cvxopt/spkg-install.in

@@ -1,20 +1,69 @@
 cd src
 
-# Stolen from Gentoo
-pkg_libs() {
-	pkg-config --libs-only-l $* | \
-		sed -e 's:[ ]-l*\(pthread\|m\)\([ ]\|$\)::g' -e 's:[ ]*$::' | \
-		tr ' ' '\n' | sort -u | sed -e "s:^-l\(.*\):\1:g" | \
-		tr '\n' ';' | sed -e 's:;$::'
-}
+# This is a POSIX (non-bash) compatible version of the same function
+# in the Gentoo cvxopt package. It's more general than it needs to
+# be right now because we may need to use the "L" and "I" modes in
+# the future to support system installations of e.g. suitesparse.
+#
+# The BLAS_LIB and LAPACK_LIB variables (among others) in cvxopt's
+# setup.py are passed in as colon-delimited strings. So, for example,
+# if your blas "l" flags are "-lblas -lcblas", then cvxopt wants
+# "blas;cblas" for BLAS_LIB.
+#
+# The following function takes a flag type ("l", "L", or "I") as its
+# first argument and a list of packages as its remaining arguments. It
+# outputs a list of libraries, library paths, or include paths,
+# respectively, for the given packages, retrieved using pkg-config and
+# deduplicated, in the appropriate format.
+#
+cvxopt_output() {
+    FLAGNAME="${1}"
+    shift
+    PACKAGES="${@}"
+
+    case "${FLAGNAME}" in
+	l) PKGCONFIG_MODE="--libs-only-l";;
+	L) PKGCONFIG_MODE="--libs-only-L";;
+	I) PKGCONFIG_MODE="--cflags-only-I";;
+	*) echo "invalid flag name: ${FLAGNAME}"; exit 1;;
+    esac
+
+    CVXOPT_OUTPUT=""
+    for PKGCONFIG_ITEM in $(pkg-config ${PKGCONFIG_MODE} ${PACKAGES}); do
+	# First strip off the leading "-l", "-L", or "-I", and replace
+	# it with a semicolon...
+	PKGCONFIG_ITEM=";${PKGCONFIG_ITEM#-${FLAGNAME}}"
 
+	# Now check to see if this element is already present in the
+	# list, and skip it if it is. This eliminates multiple entries
+	# from winding up in the list when multiple package arguments are
+	# passed to this function.
+	if [ "${CVXOPT_OUTPUT}" != "${CVXOPT_OUTPUT%${PKGCONFIG_ITEM}}" ]
+	then
+	    # It was already the last entry in the list, so skip it.
+	    continue
+	elif [ "${CVXOPT_OUTPUT}" != "${CVXOPT_OUTPUT%${PKGCONFIG_ITEM};*}" ]
+	then
+	    # It was an earlier entry in the list. These two cases are
+	    # separate to ensure that we can e.g. find ";m" at the end
+	    # of the list, but that we don't find ";metis" in the process.
+	    continue
+	fi
+
+	# It isn't in the list yet, so append it.
+	CVXOPT_OUTPUT="${CVXOPT_OUTPUT}${PKGCONFIG_ITEM}"
+    done
+
+    # Strip the leading ";" from ";foo;bar" before output.
+    echo "${CVXOPT_OUTPUT#;}"
+}
 
 # configure cvxopt by variables
 # Note that *_INC_DIR variables have to be non-empty.
 # Compilers don't like "-I ".
-export CVXOPT_BLAS_LIB="$(pkg_libs blas)"
+export CVXOPT_BLAS_LIB="$(cvxopt_output l blas)"
 export CVXOPT_BLAS_LIB_DIR="$(pkg-config --variable=libdir blas)"
-export CVXOPT_LAPACK_LIB="$(pkg_libs lapack)"
+export CVXOPT_LAPACK_LIB="$(cvxopt_output l lapack)"
 
 if test "x$SAGE_SUITESPARSE_LOCALINSTALL" != "x"; then
    export CVXOPT_SUITESPARSE_LIB_DIR="${SAGE_LOCAL}"