Use the system declared in the cross-env in the cmake_cross_file template.

Cmake use the 'Windows' name to detect we are building to Windows but
meson use the lowered 'windows' string.
So we need to lower the system declared in the cross-env when generating
the meson cross_file.

kiwix-build.py

@@ -116,7 +116,8 @@ class TargetInfo:
                 'extra_libs': ['-lwinmm', '-lws2_32', '-lshlwapi', '-lrpcrt4', '-lmsvcr90'],
                 'extra_cflags': ['-DWIN32'],
                 'host_machine': {
-                    'system': 'windows',
+                    'system': 'Windows',
+                    'lsystem': 'windows',
                     'cpu_family': 'x86',
                     'cpu': 'i686',
                     'endian': 'little'
@@ -148,6 +149,7 @@ class AndroidTargetInfo(TargetInfo):
             'extra_cflags': [],
             'host_machine': {
                 'system': 'Android',
+                'lsystem': 'android',
                 'cpu_family': self.arch,
                 'cpu': self.cpu,
                 'endian': 'little'

templates/cmake_cross_file.txt

@@ -1,5 +1,5 @@
-SET(CMAKE_SYSTEM_NAME Windows)
-SET(CMAKE_SYSTEM_PROCESSOR x86)
+SET(CMAKE_SYSTEM_NAME {host_machine[system]})
+SET(CMAKE_SYSTEM_PROCESSOR {host_machine[cpu_family]})
 
 # specify the cross compiler
 SET(CMAKE_C_COMPILER "{toolchain.binaries[CC]}")

templates/meson_cross_file.txt

@@ -14,5 +14,5 @@ cpp_args = {extra_cflags!r}
 [host_machine]
 cpu_family = '{host_machine[cpu_family]}'
 cpu = '{host_machine[cpu]}'
-system = '{host_machine[system]}'
+system = '{host_machine[lsystem]}'
 endian = '{host_machine[endian]}'