[ffmpeg] fix cross builds on windows host (microsoft#34657)

Two issues:

* we should get msys2 when building on windows, not targeting windows.
* removed usage of LIBRARY_PATH since it is ignored when cross-compiling [1].

Tested building for android on windows and works fine.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html#index-LIBRARY_005fPATH

ports/ffmpeg/portfile.cmake

@@ -33,18 +33,9 @@ if(NOT VCPKG_TARGET_ARCHITECTURE STREQUAL "wasm32")
     vcpkg_add_to_path("${NASM_EXE_PATH}")
 endif()
 
-if(VCPKG_TARGET_IS_WINDOWS AND NOT VCPKG_TARGET_IS_MINGW)
-    #We're assuming that if we're building for Windows we're using MSVC
-    set(INCLUDE_VAR "INCLUDE")
-    set(LIB_PATH_VAR "LIB")
-else()
-    set(INCLUDE_VAR "CPATH")
-    set(LIB_PATH_VAR "LIBRARY_PATH")
-endif()
-
 set(OPTIONS "--enable-pic --disable-doc --enable-debug --enable-runtime-cpudetect --disable-autodetect")
 
-if(VCPKG_TARGET_IS_WINDOWS)
+if(VCPKG_HOST_IS_WINDOWS)
     vcpkg_acquire_msys(MSYS_ROOT PACKAGES automake1.16)
     set(SHELL "${MSYS_ROOT}/usr/bin/bash.exe")
     vcpkg_add_to_path("${MSYS_ROOT}/usr/share/automake-1.16")
@@ -94,8 +85,6 @@ string(APPEND VCPKG_COMBINED_C_FLAGS_RELEASE " -I \"${CURRENT_INSTALLED_DIR}/inc
 
 ## Setup vcpkg toolchain
 
-set(ENV_LIB_PATH "$ENV{${LIB_PATH_VAR}}")
-
 set(prog_env "")
 
 if(VCPKG_DETECTED_CMAKE_C_COMPILER)
@@ -574,8 +563,12 @@ message(STATUS "Building Options: ${OPTIONS}")
 
 # Release build
 if (NOT VCPKG_BUILD_TYPE OR VCPKG_BUILD_TYPE STREQUAL "release")
+    if (VCPKG_DETECTED_MSVC)
+        set(OPTIONS_RELEASE "${OPTIONS_RELEASE} --extra-ldflags=-libpath:\"${CURRENT_INSTALLED_DIR}/lib\"")
+    else()
+        set(OPTIONS_RELEASE "${OPTIONS_RELEASE} --extra-ldflags=-L\"${CURRENT_INSTALLED_DIR}/lib\"")
+    endif()
     message(STATUS "Building Release Options: ${OPTIONS_RELEASE}")
-    set(ENV{${LIB_PATH_VAR}} "${CURRENT_INSTALLED_DIR}/lib${VCPKG_HOST_PATH_SEPARATOR}${ENV_LIB_PATH}")
     set(ENV{PKG_CONFIG_PATH} "${CURRENT_INSTALLED_DIR}/lib/pkgconfig")
     message(STATUS "Building ${PORT} for Release")
     file(MAKE_DIRECTORY "${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-rel")
@@ -611,8 +604,12 @@ endif()
 
 # Debug build
 if (NOT VCPKG_BUILD_TYPE OR VCPKG_BUILD_TYPE STREQUAL "debug")
+    if (VCPKG_DETECTED_MSVC)
+        set(OPTIONS_DEBUG "${OPTIONS_DEBUG} --extra-ldflags=-libpath:\"${CURRENT_INSTALLED_DIR}/debug/lib\"")
+    else()
+        set(OPTIONS_DEBUG "${OPTIONS_DEBUG} --extra-ldflags=-L\"${CURRENT_INSTALLED_DIR}/debug/lib\"")
+    endif()
     message(STATUS "Building Debug Options: ${OPTIONS_DEBUG}")
-    set(ENV{${LIB_PATH_VAR}} "${CURRENT_INSTALLED_DIR}/debug/lib${VCPKG_HOST_PATH_SEPARATOR}${ENV_LIB_PATH}")
     set(ENV{LDFLAGS} "${VCPKG_COMBINED_SHARED_LINKER_FLAGS_DEBUG}")
     set(ENV{PKG_CONFIG_PATH} "${CURRENT_INSTALLED_DIR}/debug/lib/pkgconfig")
     message(STATUS "Building ${PORT} for Debug")

ports/ffmpeg/vcpkg.json

@@ -1,7 +1,7 @@
 {
   "name": "ffmpeg",
   "version": "6.0",
-  "port-version": 1,
+  "port-version": 2,
   "description": [
     "a library to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created.",
     "FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge. No matter if they were designed by some standards committee, the community or a corporation. It is also highly portable: FFmpeg compiles, runs, and passes our testing infrastructure FATE across Linux, Mac OS X, Microsoft Windows, the BSDs, Solaris, etc. under a wide variety of build environments, machine architectures, and configurations."

versions/baseline.json

@@ -2566,7 +2566,7 @@
     },
     "ffmpeg": {
       "baseline": "6.0",
-      "port-version": 1
+      "port-version": 2
     },
     "ffnvcodec": {
       "baseline": "11.1.5.2",

versions/f-/ffmpeg.json

@@ -1,5 +1,10 @@
 {
   "versions": [
+    {
+      "git-tree": "9f33fe16e3a4e278bc2eb92b24483d00b90e9f3a",
+      "version": "6.0",
+      "port-version": 2
+    },
     {
       "git-tree": "70c25989395c92bd79faf0b136fb4636e96d541c",
       "version": "6.0",