add portability variable for libtool

Makefile

@@ -16,15 +16,16 @@ TOP_DIR    := $(patsubst %/,%,$(dir $(MAKEFILE)))
 PATH       := $(PREFIX)/bin:$(PATH)
 SHELL      := bash
 INSTALL    := $(shell ginstall --help >/dev/null 2>&1 && echo g)install
+LIBTOOL    := $(shell glibtool --help >/dev/null 2>&1 && echo g)libtool
 LIBTOOLIZE := $(shell glibtoolize --help >/dev/null 2>&1 && echo g)libtoolize
 PATCH      := $(shell gpatch --help >/dev/null 2>&1 && echo g)patch
 SED        := $(shell gsed --help >/dev/null 2>&1 && echo g)sed
 VERSION    := $(shell $(SED) -n 's,^.*<span id="latest-version">\([^<]*\)</span>.*$$,\1,p' '$(TOP_DIR)/doc/index.html')
 
 REQUIREMENTS := autoconf automake bash bison bzip2 cmake flex \
-                gcc intltoolize $(LIBTOOLIZE) $(MAKE) openssl \
-                $(PATCH) $(PERL) pkg-config scons $(SED) unzip \
-                wget xz yasm
+                gcc intltoolize $(LIBTOOL) $(LIBTOOLIZE) \
+                $(MAKE) openssl $(PATCH) $(PERL) pkg-config \
+                scons $(SED) unzip wget xz yasm
 
 # unexport any environment variables that might cause trouble
 unexport AR CC CFLAGS C_INCLUDE_PATH CPATH CPLUS_INCLUDE_PATH CPP

doc/index.html

@@ -1018,6 +1018,7 @@ https://...</pre>
         <table class="translation">
             <tr><td><code>bash</code></td>      <td>&rarr;</td><td><code>$(SHELL)</code></td></tr>
             <tr><td><code>install</code></td>   <td>&rarr;</td><td><code>$(INSTALL)</code></td></tr>
+            <tr><td><code>libtool</code></td>   <td>&rarr;</td><td><code>$(LIBTOOL)</code></td></tr>
             <tr><td><code>libtoolize</code></td><td>&rarr;</td><td><code>$(LIBTOOLIZE)</code></td></tr>
             <tr><td><code>make</code></td>      <td>&rarr;</td><td><code>$(MAKE)</code></td></tr>
             <tr><td><code>patch</code></td>     <td>&rarr;</td><td><code>$(PATCH)</code></td></tr>