Issue #28573: Avoid setting up env too many times during build

PCbuild/build.bat

@@ -120,9 +120,9 @@ if "%do_pgo%"=="true" (
     @echo off
     call :Kill
     set conf=PGUpdate
+    set target=Build
 )
 goto Build
-
 :Kill
 echo on
 msbuild "%dir%\pythoncore.vcxproj" /t:KillPython %verbose%^

Tools/msi/buildrelease.bat

@@ -35,7 +35,7 @@ set BUILDX86=
 set BUILDX64=
 set TARGET=Rebuild
 set TESTTARGETDIR=
-set PGO=default
+set PGO=-m test -q --pgo
 set BUILDNUGET=1
 set BUILDZIP=1
 
@@ -109,14 +109,12 @@ exit /B 0
 @echo off
 
 if "%1" EQU "x86" (
-    call "%PCBUILD%env.bat" x86
     set PGO=
     set BUILD=%PCBUILD%win32\
     set BUILD_PLAT=Win32
     set OUTDIR_PLAT=win32
     set OBJDIR_PLAT=x86
 ) else (
-    call "%PCBUILD%env.bat" amd64
     set BUILD=%PCBUILD%amd64\
     set PGO=%~2
     set BUILD_PLAT=x64
@@ -143,37 +141,18 @@ if not "%CERTNAME%" EQU "" (
 )
 
 if not "%SKIPBUILD%" EQU "1" (
-    @call "%PCBUILD%build.bat" -e -p %BUILD_PLAT% -d -t %TARGET% %CERTOPTS%
+    if "%PGO%" EQU "" (
+        set PGOOPTS=
+    ) else (
+        set PGOOPTS=--pgo --pgojob "%PGO%"
+    )
+    @call "%PCBUILD%build.bat" -e -p %BUILD_PLAT% -t %TARGET% %CERTOPTS% %PGOOPTS%
     @if errorlevel 1 exit /B
     @rem build.bat turns echo back on, so we disable it again
     @echo off
-    
-    if "%PGO%" EQU "" (
-        @call "%PCBUILD%build.bat" -e -p %BUILD_PLAT% -t %TARGET% %CERTOPTS%
-    ) else (
-        @call "%PCBUILD%build.bat" -e -p %BUILD_PLAT% -c PGInstrument -t %TARGET% %CERTOPTS%
-        @if errorlevel 1 exit /B
-        
-        @del "%BUILD%*.pgc"
-        if "%PGO%" EQU "default" (
-            "%BUILD%python.exe" -m test -q --pgo
-        ) else if "%PGO%" EQU "default2" (
-            "%BUILD%python.exe" -m test -r -q --pgo
-            "%BUILD%python.exe" -m test -r -q --pgo
-        ) else if "%PGO%" EQU "default10" (
-            for /L %%i in (0, 1, 9) do "%BUILD%python.exe" -m test -q -r --pgo
-        ) else if "%PGO%" EQU "pybench" (
-            "%BUILD%python.exe" "%PCBUILD%..\Tools\pybench\pybench.py"
-        ) else (
-            "%BUILD%python.exe" %PGO%
-        )
-        
-        @call "%PCBUILD%build.bat" -e -p %BUILD_PLAT% -c PGUpdate -t Build %CERTOPTS%
-    )
-    @if errorlevel 1 exit /B
-    @echo off
 )
 
+call "%PCBUILD%env.bat"
 if "%OUTDIR_PLAT%" EQU "win32" (
     msbuild "%D%launcher\launcher.wixproj" /p:Platform=x86 %CERTOPTS% /p:ReleaseUri=%RELEASE_URI%
     if errorlevel 1 exit /B
@@ -222,10 +201,9 @@ echo    --build (-b)        Incrementally build Python rather than rebuilding
 echo    --skip-build (-B)   Do not build Python (just do the installers)
 echo    --skip-doc (-D)     Do not build documentation
 echo    --pgo               Specify PGO command for x64 installers
-echo    --skip-pgo          Build x64 installers using PGO
+echo    --skip-pgo          Build x64 installers without using PGO
 echo    --skip-nuget        Do not build Nuget packages
 echo    --skip-zip          Do not build embeddable package
-echo    --pgo               Build x64 installers using PGO
 echo    --download          Specify the full download URL for MSIs
 echo    --test              Specify the test directory to run the installer tests
 echo    -h                  Display this help information
@@ -233,13 +211,8 @@ echo.
 echo If no architecture is specified, all architectures will be built.
 echo If --test is not specified, the installer tests are not run.
 echo.
-echo For the --pgo option, any Python command line can be used as well as the
+echo For the --pgo option, any Python command line can be used, or 'default' to
-echo following shortcuts:
+echo use the default task (-m test --pgo).
-echo     Shortcut        Description
-echo     default         Test suite with --pgo
-echo     default2        2x test suite with --pgo and randomized test order
-echo     default10       10x test suite with --pgo and randomized test order
-echo     pybench         pybench script
 echo.
 echo The following substitutions will be applied to the download URL:
 echo     Variable        Description         Example