This build was failing with errors in libgit2-1.8.0/utils/src/utils/process.h and now it's working. These are the only changes I made and you can see they're very minimal with no reason why they'd start suddenly working.

PPP3/reset_build.ps1

@@ -2,10 +2,13 @@ mv .\subprojects\packagecache .
 rm -recurse -force .\subprojects\,.\builddir\
 mkdir subprojects
 mv .\packagecache .\subprojects\
+cp *.wrap subprojects
+# cp -recurse -force packagefiles subprojects
 mkdir builddir
 meson wrap install fmt
 meson wrap install sqlite3
 meson wrap install sqlitecpp
 meson wrap install ftxui
-# meson setup -Ddefault_library=static builddir
-meson setup builddir
+# $env:CC="clang"
+# $env:CXX="clang++"
+meson setup -Ddefault_library=static builddir

PPP3/setup.ps1

@@ -4,4 +4,5 @@ meson wrap install fmt
 meson wrap install sqlite3
 meson wrap install sqlitecpp
 meson wrap install ftxui
+cp *.wrap subprojects
 meson setup -Ddefault_library=static builddir

PPP3/watchgit.cpp

@@ -17,6 +17,8 @@
 using namespace std;
 using namespace fmt;
 
+#define BUF_MAX 1024
+
 /*
  * No idea what the semantics of this are.  Will need
  * to research git's dumb terminology to figure out why
@@ -124,7 +126,7 @@ void list_git_changes(git_repository* repo) {
 
 void run_build(const char* command) {
   regex err_re("(.*?):([0-9]+):([0-9]+):\\s*(.*?):\\s*(.*)");
-  char buffer[LINE_MAX]; // LINE_MAX is a define already?
+  char buffer[BUF_MAX]; // BUF_MAX is a define already?
   smatch err;
   ofstream stats_out;
   stats_out.open("stats.csv", ios::out | ios::app);
@@ -137,7 +139,7 @@ void run_build(const char* command) {
   FILE *build_out = popen(command, "r");
   dbc::check(build_out != nullptr, "Failed to run command.");
 
-  while(fgets(buffer, LINE_MAX, build_out) != nullptr) {
+  while(fgets(buffer, BUF_MAX, build_out) != nullptr) {
     string line(buffer);  // yeah, that's probably a problem
 
     print("{}\n", line);