Index: lib/configure
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/bin/sh
 
 CONFIG="config.mk"
 PREFIX="/usr/local"
@@ -80,7 +80,7 @@
 
 # If someone runs sudo make install as very first command, and configure later,
 # $CONFIG cannot be overwritten, and must be deleted before continuing.
-if [[ -f "$CONFIG" && ! -w "$CONFIG" ]]; then
+if [ -f "$CONFIG" -a ! -w "$CONFIG" ]; then
     echo "Cannot overwrite file $CONFIG! Please delete it."
     exit 1
 fi
@@ -135,10 +135,8 @@
 
 # SSE
 if [ "$SSE" = 'auto' ]; then
-    if [[ "$(uname -m)" =~ (amd|x86_)64 ||
-          "$(grep -E -m1 "^flags" /proc/cpuinfo)" =~ "sse" ]]; then
-        SSE=1
-    fi
+    echo $(uname -m) | grep -E -q '(amd|x86_)64' && SSE=1
+    grep -E -m1 -q '^flags.*sse' /proc/cpuinfo 2>/dev/null && SSE=1
 fi
 
 if [ "$SSE" -eq 1 ]; then
@@ -161,9 +159,8 @@
     else
         OPENMPFLAGS="-fopenmp"
     fi
-    if [[ "$("$CC" -xc -E $OPENMPFLAGS <(echo "#ifdef _OPENMP
-           #include <omp.h>
-           #endif") 2>&1)" =~ "omp_get_thread_num" ]]; then
+    if echo "$(printf '#ifdef _OPENMP\n#include <omp.h>\n#endif\n' | \
+        "$CC" -xc -E $OPENMPFLAGS - 2>&1)" | grep -q omp_get_thread_num; then
         cflags "$OPENMPFLAGS"
         lflags "$OPENMPFLAGS"
         status "OpenMP" "yes"