Need help with postgresql build on windows

I have started exploring Postgresql recently. 

I am trying to build Postgresql from source on a windows machine. I am referring to the page https://www.postgresql.org/docs/current/install-meson.html#INSTALL-SHORT-MESON

The ninja command is failing with the error message:

PS C:\PostgreSQLworkspace\postgres\build> ninja
[142/2102] Generating src/fe_utils/psqlscan with a custom command                
FAILED: src/fe_utils/psqlscan.c
"C:\MyPrograms\Meson\meson.exe" "runpython" "../src/tools/pgflex" "--builddir" "." "--srcdir" ".." "--privatedir" "src/fe_utils/psqlscan.c.p" "--flex" "C:\MyPrograms\GnuWin32\bin\flex.EXE" "--perl" "C:\Strawberry\perl\bin\perl.EXE" "-i" "../src/fe_utils/psqlscan.l" "-o" "src/fe_utils/psqlscan.c" "--no-backup" "--" "-Cfe" "-p" "-p"
C:\MyPrograms\GnuWin32\bin\flex.EXE: can't open C:\PostgreSQLworkspace\postgres\build\src\fe_utils\psqlscan.c
[146/2102] Generating src/backend/bootstrap/bootscanner with a custom command    
FAILED: src/backend/bootstrap/bootscanner.c
"C:\MyPrograms\Meson\meson.exe" "runpython" "../src/tools/pgflex" "--builddir" "." "--srcdir" ".." "--privatedir" "src/backend/bootstrap/bootscanner.c.p" "--flex" "C:\MyPrograms\GnuWin32\bin\flex.EXE" "--perl" "C:\Strawberry\perl\bin\perl.EXE" "-i" "../src/backend/bootstrap/bootscanner.l" "-o" "src/backend/bootstrap/bootscanner.c"
C:\MyPrograms\GnuWin32\bin\flex.EXE: can't open C:\PostgreSQLworkspace\postgres\build\src\backend\bootstrap\bootscanner.c
[147/2102] Generating src/backend/parser/scan with a custom command
FAILED: src/backend/parser/scan.c
"C:\MyPrograms\Meson\meson.exe" "runpython" "../src/tools/pgflex" "--builddir" "." "--srcdir" ".." "--privatedir" "src/backend/parser/scan.c.p" "--flex" "C:\MyPrograms\GnuWin32\bin\flex.EXE" "--perl" "C:\Strawberry\perl\bin\perl.EXE" "-i" "../src/backend/parser/scan.l" "-o" "src/backend/parser/scan.c" "--no-backup" "--" "-CF" "-p" "-p"
C:\MyPrograms\GnuWin32\bin\flex.EXE: can't open C:\PostgreSQLworkspace\postgres\build\src\backend\parser\scan.c
ninja: build stopped: subcommand failed.
PS C:\PostgreSQLworkspace\postgres\build>

I have enabled full permission on the folder but still no luck.

Can someone please help me with this? Any troubleshooting pointers would be a great help!

Thanks in advance!

Thanks and Regards,

Prafulla