use os.sh for more functionality.

binding.gyp

@@ -10,10 +10,8 @@
       ' && echo "$LEVELDB_INCLUDE"'\
       ' || test "$BITCOIN_DIR" && echo "${BITCOIN_DIR}/src/leveldb/include"' \
       ' || echo ./include)',
-      'BITCOIN_DIR': '<!(test -n "$BITCOIN_DIR"'\
-        ' && echo "$BITCOIN_DIR"'\
-        ' || echo "${HOME}/bitcoin")',
-      'LIBBITCOIND': '<!(./platform/os.sh)',
+      'BITCOIN_DIR': '<!(./platform/os.sh btcdir)',
+      'LIBBITCOIND': '<!(./platform/os.sh lib)',
     },
     'defines': [
       'ENABLE_WALLET=1',

build-libbitcoind.sh

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 cur_dir="$(pwd)"
-os_dir=$(dirname "$(./platform/os.sh)")
+os_dir=$(./platform/os.sh osdir)
 
 if test -e "${os_dir}/libbitcoind.so"; then
   read -r -p 'libbitcoind.so already built. Rebuild? (Y/n): ' choice

platform/os.sh

@@ -1,7 +1,13 @@
 #!/bin/bash
 
-if test -n "$BITCOIN_DIR" -a -e "${BITCOIN_DIR}/src/libbitcoind.so"; then
-  echo -n "${BITCOIN_DIR}/src/libbitcoind.so"
+if test x"$1" = x'btcdir'; then
+  if test -n "$BITCOIN_DIR"; then
+    echo "$BITCOIND_DIR"
+  elif test -d "$(pwd)/libbitcoind"; then
+    echo "$(pwd)/libbitcoind"
+  elif test -d "${HOME}/bitcoin"; then
+    echo "${HOME}/bitcoin"
+  fi
   exit 0
 fi
 
@@ -43,4 +49,16 @@ if test -z "$os"; then
   fi
 fi
 
-echo -n "$(pwd)/platform/${os}/libbitcoind.so"
+if test x"$1" = x'osdir'; then
+  echo -n "$(pwd)/platform/${os}"
+  exit 0
+fi
+
+if test -z "$1" -o x"$1" = x'lib'; then
+  if test -n "$BITCOIN_DIR" -a -e "${BITCOIN_DIR}/src/libbitcoind.so"; then
+    echo -n "${BITCOIN_DIR}/src/libbitcoind.so"
+  else
+    echo -n "$(pwd)/platform/${os}/libbitcoind.so"
+  fi
+  exit 0
+fi