Update instructions for cross-compile.

INSTALL_WINDOWS

@@ -1,13 +1,11 @@
-Instructions for compiling cpuminer-opt for Windows.
+Instructions for compiling cpuminer-gr for Windows.
 
-Thwaw intructions nay be out of date. Please consult the wiki for
+The instructions may be out of date. Please consult the wiki for
 the latest:
 
-https://github.com/JayDDee/cpuminer-opt/wiki/Compiling-from-source
-
 Windows compilation using Visual Studio is not supported. Mingw64 is
 used on a Linux system (bare metal or virtual machine) to cross-compile
-cpuminer-opt executable binaries for Windows.
+cpuminer-gr executable binaries for Windows.
 
 These instructions were written for Debian and Ubuntu compatible distributions
 but should work on other major distributions as well. However some of the
@@ -84,19 +82,20 @@ Define some local variables to point to local library.
 
 $ export LOCAL_LIB="$HOME/usr/lib"
 
-$ export LDFLAGS="-L$LOCAL_LIB/curl/lib/.libs -L$LOCAL_LIB/gmp/.libs -L$LOCAL_LIB/openssl"
-
 $ export CONFIGURE_ARGS="--with-curl=$LOCAL_LIB/curl --with-crypto=$LOCAL_LIB/openssl --host=x86_64-w64-mingw32"
 
+$ export MINGW_LIB="/usr/x86_64-w64-mingw32/lib"
+
 Adjust for gcc version:
 
 $ export GCC_MINGW_LIB="/usr/lib/gcc/x86_64-w64-mingw32/9.3-win32"
+                                                        10-win32
 
 Create a release directory and copy some dll files previously built. This can be done outside of cpuminer-opt and only needs to be done once. If the release directory is in cpuminer-opt directory it needs to be recreated every time a source package is decompressed.
 
 $ mkdir release
-$ cp /usr/x86_64-w64-mingw32/lib/zlib1.dll release/
-$ cp /usr/x86_64-w64-mingw32/lib/libwinpthread-1.dll release/
+$ cp $MINGW_LIB/zlib1.dll release/
+$ cp $MINGW_LIB/libwinpthread-1.dll release/
 $ cp $GCC_MINGW_LIB/libstdc++-6.dll release/
 $ cp $GCC_MINGW_LIB/libgcc_s_seh-1.dll release/
 $ cp $LOCAL_LIB/openssl/libcrypto-1_1-x64.dll release/
@@ -112,28 +111,42 @@ location. .zip or .tar.gz, your choice.
 
 https://github.com/WyvernTKC/cpuminer-gr-avx2/releases
 
-Decompress and change to the cpuminer-opt directory.
+$ git clone https://github.com/WyvernTKC/cpuminer-gr-avx2 cpuminer-gr
+
+Decompress and change to the cpuminer-gr directory.
 
 6. compile
 
 Create a link to the locally compiled version of gmp.h
 
-$ ln -s $LOCAL_LIB/gmp-version/gmp.h ./gmp.h
+$ export LDFLAGS="-L$LOCAL_LIB/curl/lib/.libs -L$LOCAL_LIB/gmp/.libs -L$LOCAL_LIB/openssl"
+
+$ rm ./gmp.h 2>/dev/null
+$ ln -s $LOCAL_LIB/gmp/gmp.h ./gmp.h
 
+$ make distclean
+$ rm -f config.status
 $ ./autogen.sh
 
 Configure the compiler for the CPU architecture of the host machine:
 
+$ export DCFLAGS="-fno-common -D_WIN32_WINNT=0x0601"
+
 For GCC-10+:
-CFLAGS="-O3 -march=native -mtune=native" CXXFLAGS="$CFLAGS -std=c++20 -Wno-ignored-attributes" ./configure --with-curl
+CFLAGS="-O3 -march=native -mtune=native ${DCFLAGS}" \
+CXXFLAGS="$CFLAGS -std=c++20 -Wno-ignored-attributes" \
+./configure ${CONFIGURE_ARGS}
+
 For GCC-8 && GCC-9:
-CFLAGS="-O3 -march=native -mtune=native" CXXFLAGS="$CFLAGS -std=c++2a -fconcepts -Wno-ignored-attributes" ./configure --with-curl
+CFLAGS="-O3 -march=native -mtune=native ${DCFLAGS}" \
+CXXFLAGS="$CFLAGS -std=c++2a -fconcepts -Wno-ignored-attributes" \
+./configure ${CONFIGURE_ARGS}
 
 You can find several examples in README.txt
 
 Once you have run configure successfully run the compiler with n CPU threads:
 
-$ make -j n
+$ make -j $(nproc)
 
 Copy cpuminer.exe to the release directory, compress and copy the release directory to a Windows system and run cpuminer.exe from the command line.
 
@@ -142,9 +155,3 @@ Run cpuminer
 In a command windows change directories to the unzipped release folder. to get a list of all options:
 
 cpuminer.exe --help
-
-Command options are specific to where you mine. Refer to the pool's instructions on how to set them.
-
-Create a link to the locally compiled version of gmp.h
-
-$ ln -s $LOCAL_LIB/gmp-version/gmp.h ./gmp.h