GCC 4.9.1无法找到可用的ISL

正在尝试在CentOS6.5（x86_64）上从源代码配置/build gcc 4.9.1

/configure看起来像：

mkdir ../gcc-build && cd ../gcc-build && ../gcc-4.9.1/configure 
LDFLAGS="-L/usr/local/lib, -L/usr/local/lib/cloog.isl, **-L/opt/x86_64/isl-0.12.2/lib**, 
-L/usr/local/lib/itcl4.0.1, -L/usr/local/lib/libffi-3.0.13, -L/usr/local/lib/pkgconfig, 
-L/usr/local/lib/sqlite3.8.6, -L/usr/local/lib/tcl8.6, -L/usr/local/lib/tdbc1.0.1, 
-L/usr/local/lib/tdbcmysql1.0.1, -L/usr/local/lib/tdbcodbc1.0.1, 
-L/usr/local/lib/tdbcpostgres1.0.1, -L/usr/local/lib/thread2.7.1, -L/usr/local/lib/tk8.6, 
-L/usr/local/lib64, -L/usr/lib64, -L/lib64, -L/usr/lib, -L/lib" CFLAGS="-I/usr/local/include, 
-I/usr/local/include/atomic_ops, -I/usr/local/include/autoopts, -I/usr/local/include/cloog, 
**-I/opt/x86_64/isl-0.12.2/include**, -I/usr/local/include/freetype2, -I/usr/local/include/gc, 
-I/usr/local/include/libpng16" --prefix=/opt/x86_64/gcc-4.9.1 --disable-multilib 
--disable-libada --with-system-zlib --with-libiconv-prefix=/usr/local/lib 
--with-mpc-include=/usr/local/include --with-mpc-lib=/usr/local/lib 
--with-mpfr-include=/usr/local/include --with-mpfr-lib=/usr/local/lib 
--with-gmp-include=/usr/local/include --with-gmp-lib=/usr/local/lib 
--with-isl=/opt/x86_64/isl-0.12.2 --with-cloog=/opt/x86_64/cloog-0.18.1 --disable-libsanitizer 
--disable-libssp --disable-libquadmath --disable-libquadmath-support --enable-shared 
--enable-threads=posix --enable-libstdcxx --enable-__cxa_atexit --enable-clocale=gnu 
--enable-languages=c,c++,objc,obj-c++

但它在以下方面失败了：

• 正在检查gmp/mpfr/mpc库的正确版本。。。对
• 正在检查ISL的版本0.10。。。没有
• 正在检查ISL的版本0.11。。。没有
• 正在检查ISL的版本0.12。。。没有
• 配置：错误：找不到可用的ISL。有关详细信息，请参阅config.log 细节

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我不知道如何声明ISL路径，它也在我的LD_LIBRARY_path

中。事实上，您看过config.log了吗？它将包含测试编译的程序主体以及编译器/链接器对此的投诉。解决方案将立即出台。