FindECW.cmake always finds x64 libs on x64 Windows host

[mpdaly]

Expected behavior and actual behavior.

Expected: building GDAL as Win32/x86 should find the Win32 ECW SDK .lib-s, independent of the host platform architecture

Actual: FindECW.cmake always finds the x64 ECW SDK .lib-s on 64-bit host

Steps to reproduce the problem.

With native x86 tools

• On 64-bit Windows, open the x86 Tools Command Prompt for VS 2022
• Run CMake w/ ECW SDK enabled via ECW_ROOT=<path_to_ERDAS_ECW_JPEG_2000_SDK>

The output includes (with added debugging info):

-- CMAKE_SYSTEM_PROCESSOR=AMD64
-- ECW_ARCH=x64
-- Found ECW: <path_to_ERDAS_ECW_JPEG_2000_SDK>/lib/vc141/x64/NCSEcw.lib (found version "5.5")

With x64-to-x86 cross-compiling tools

• On 64-bit Windows, open the x64_x86 Tools Command Prompt for VS 2022
• Run CMake w/ ECW SDK enabled via ECW_ROOT=<path_to_ERDAS_ECW_JPEG_2000_SDK>

The output includes (with added debugging info):

-- CMAKE_SYSTEM_PROCESSOR=AMD64
-- ECW_ARCH=x64
-- Found ECW: <path_to_ERDAS_ECW_JPEG_2000_SDK>/lib/vc141/x64/NCSEcw.lib (found version "5.5")

In both cases the x64 folder is found, not the Win32.

The CMake documentation specifically warns against using CMAKE_SYSTEM_PROCESSOR.

Operating system

Windows 11 64-bit, w/ VS 2022

GDAL version and provenance

3.6 and later, 3.5 if building w/ CMake