436: rm the existing extension before cp the new one

It seems that directly copying the new .so over the old one is slightly
different to rm the old .so then copying the new one. This fixes a segfault
that was observed when an existing ext was already in the ext directory. This
didn't manifest before, because `make install` (the approach used by compiling
from source) uses basically:

    $extSrcPath/build/shtool --debug install -c {$extSrcPath}modules/* $dest

This is a shell script, and ultimately it boils down to:

 - cp (or mv) the .so to a temp file in the dest path
 - rm the dest file
 - mv the temp file to the dest file

It was observed that this approach did not cause the segfault, but previous to
this commit, PIE was only doing:

 - cp the .so to the dest file

It seems there is some much lower-level differences in how these operations
affect the running processes, so this commit changes PIE to `rm` the target
file if it already exists first, which seems to solve the issue.

Author: asgrim

src/Installing/UnixInstall.php

@@ -14,7 +14,8 @@
 use RuntimeException;
 use Webmozart\Assert\Assert;
 
-use function array_unshift;
+use function array_map;
+use function array_merge;
 use function file_exists;
 use function implode;
 use function is_writable;
@@ -45,18 +46,29 @@ public function __invoke(
             $sharedObjectName,
         );
 
+        $installCommands = [];
         switch (DownloadUrlMethod::fromDownloadedPackage($downloadedPackage)) {
             case DownloadUrlMethod::PrePackagedBinary:
                 Assert::notNull($builtBinaryFile);
-                $installCommand = [
+
+                if (file_exists($expectedSharedObjectLocation)) {
+                    $installCommands[] = [
+                        'rm',
+                        '-v',
+                        $expectedSharedObjectLocation,
+                    ];
+                }
+
+                $installCommands[] = [
                     'cp',
+                    '-v',
                     $builtBinaryFile->filePath,
                     $targetExtensionPath,
                 ];
                 break;
 
             default:
-                $installCommand = ['make', 'install'];
+                $installCommands[] = ['make', 'install'];
         }
 
         // If the target directory isn't writable, or a .so file already exists and isn't writable, try to use sudo
@@ -71,18 +83,20 @@ public function __invoke(
                 '<comment>Cannot write to %s, so using sudo to elevate privileges.</comment>',
                 $targetExtensionPath,
             ));
-            array_unshift($installCommand, Sudo::find());
+            $installCommands = array_map(static fn (array $command) => array_merge(['sudo'], $command), $installCommands);
         }
 
-        $io->write(sprintf('<info>Install command is: %s</info>', implode(' ', $installCommand)), verbosity: IOInterface::VERY_VERBOSE);
+        $io->write(sprintf('<info>Install commands are: %s</info>', implode(', ', array_map(static fn (array $command) => implode(' ', $command), $installCommands))), verbosity: IOInterface::VERY_VERBOSE);
 
-        $makeInstallOutput = Process::run(
-            $installCommand,
-            $downloadedPackage->extractedSourcePath,
-            self::MAKE_INSTALL_TIMEOUT_SECS,
-        );
+        foreach ($installCommands as $installCommand) {
+            $makeInstallOutput = Process::run(
+                $installCommand,
+                $downloadedPackage->extractedSourcePath,
+                self::MAKE_INSTALL_TIMEOUT_SECS,
+            );
 
-        $io->write($makeInstallOutput, verbosity: IOInterface::VERY_VERBOSE);
+            $io->write($makeInstallOutput, verbosity: IOInterface::VERY_VERBOSE);
+        }
 
         if (! file_exists($expectedSharedObjectLocation)) {
             throw new RuntimeException('Install failed, ' . $expectedSharedObjectLocation . ' was not installed.');